"size" function nodes down from 454 to 321

Also removes some broken list library functions

.gitignore

@@ -9,3 +9,4 @@
 WD
 bin/
 dist*
+.tricu_history

README.md

@@ -2,37 +2,31 @@
 
 ## Introduction
 
-tricu (pronounced "tree-shoe") is a purely functional interpreted language implemented in Haskell. It is fundamentally based on the application of [Tree Calculus](https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf) terms, but minimal syntax sugar is included to provide a useful programming tool. 
+tricu (pronounced "tree-shoe") is a purely functional interpreted language implemented in Haskell. It is fundamentally based on the application of [Tree Calculus](https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf) terms, but minimal syntax sugar is included.
 
-*tricu is under active development and you should expect breaking changes with every commit.*
+*This experiment has concluded. tricu will see no further development or bugfixes.*
 
 tricu is the word for "tree" in Lojban: `(x1) is a tree of species/cultivar (x2)`.
 
-## Features
+## Acknowledgements 
 
-- Tree Calculus operator: `t`
+Tree Calculus was discovered by [Barry Jay](https://github.com/barry-jay-personal/blog). 
-- Assignments: `x = t t`
+
-- Immutable definitions
+[treecalcul.us](https://treecalcul.us) is an excellent website with an intuitive Tree Calculus code playground created by [Johannes Bader](https://johannes-bader.com/) that introduced me to Tree Calculus.
-- Lambda abstraction syntax: `id = (\a : a)`
-- List, Number, and String literals: `[(2) ("Hello")]` 
-- Function application: `not (not false)`
-- Higher order/first-class functions: `map (\a : append a "!") [("Hello")]`
-- Intensionality blurs the distinction between functions and data (see REPL examples)
-- Simple module system for code organization
 
 ## REPL examples
 
 ```
 tricu < -- Anything after `--` on a single line is a comment
-tricu < id = (\a : a) -- Lambda abstraction is eliminated to tree calculus terms
+tricu < id = (a : a) -- Lambda abstraction is eliminated to tree calculus terms
-tricu < head (map (\i : append i " world!") [("Hello, ")])
+tricu < head (map (i : append i " world!") [("Hello, ")])
 tricu > "Hello,  world!"
-tricu < id (head (map (\i : append i " world!") [("Hello, ")]))
+tricu < id (head (map (i : append i " world!") [("Hello, ")]))
 tricu > "Hello,  world!"
 
 tricu < -- Intensionality! We can inspect the structure of a function or data.
-tricu < triage = (\a b c : t (t a b) c)
+tricu < triage = (a b c : t (t a b) c)
-tricu < test = triage "Leaf" (\z : "Stem") (\a b : "Fork")
+tricu < test = triage "Leaf" (z : "Stem") (a b : "Fork")
 tricu < test (t t)
 tricu > "Stem"
 tricu < -- We can even convert a term back to source code (/demos/toSource.tri)
@@ -41,13 +35,21 @@ tricu > "(t (t (t t) (t t t)) (t t (t t t)))"
 tricu < -- or calculate its size (/demos/size.tri)
 tricu < size not?
 tricu > 12
+
+tricu < -- REPL Commands:
+tricu < !definitions  -- Lists all available definitions
+tricu < !output       -- Change output format (Tree, FSL, AST, etc.)
+tricu < !import       -- Import definitions from a file
+tricu < !exit         -- Exit the REPL
+tricu < !clear        -- ANSI screen clear
+tricu < !save         -- Save all REPL definitions to a file that you can !import
+tricu < !reset        -- Clear all REPL definitions
+tricu < !version      -- Print tricu version
 ```
 
 ## Installation and Use
 
-[Releases are available for Linux.](https://git.eversole.co/James/tricu/releases)
+You can easily build and run this project using [Nix](https://nixos.org/download/).
-
-Or you can easily build and run this project using [Nix](https://nixos.org/download/).
 
 - Quick Start (REPL): 
   - `nix run git+https://git.eversole.co/James/tricu`
@@ -83,9 +85,3 @@ tricu decode [OPTIONS]
   -f --file=FILE  Optional input file path to attempt decoding.
                     Defaults to stdin.
 ```
-
-## Acknowledgements 
-
-Tree Calculus was discovered by [Barry Jay](https://github.com/barry-jay-personal/blog). 
-
-[treecalcul.us](https://treecalcul.us) is an excellent website with an intuitive Tree Calculus code playground created by [Johannes Bader](https://johannes-bader.com/) that introduced me to Tree Calculus.

demos/equality.tri

@@ -1,4 +1,5 @@
-!import "lib/base.tri" !Local
+!import "../lib/base.tri" !Local
+!import "../lib/list.tri" !Local
 
 main = lambdaEqualsTC
 
@@ -10,20 +11,17 @@ demo_true  = t t
 not_TC?     = t (t (t t) (t t t)) (t t (t t t))
 
 -- /demos/toSource.tri contains an explanation of `triage`
-demo_triage = \a b c : t (t a b) c
+demo_triage = a b c : t (t a b) c
-demo_matchBool = (\ot of : demo_triage
+demo_matchBool = a b : demo_triage b (_ : a) (_ _ : a)
-  of
+
-  (\_ : ot)
-  (\_ _ : ot)
-)
 -- Lambda representation of the Boolean `not` function
 not_Lambda? = demo_matchBool demo_false demo_true
 
--- Since tricu eliminates Lambda terms to SKI combinators, the tree form of many
+-- As tricu eliminates Lambda terms to SKI combinators, the tree form of many
 -- functions defined via Lambda terms are larger than the most efficient TC
--- representation. Between different languages that evaluate to tree calculus 
+-- representation possible. Between different languages that evaluate to tree
--- terms, the exact implementation of Lambda elimination may differ and lead 
+-- calculus terms, the exact implementation of Lambda elimination may differ
--- to different tree representations even if they share extensional behavior.
+-- and lead to different trees even if they share extensional behavior.
 
 -- Let's see if these are the same:
 lambdaEqualsTC = equal? not_TC? not_Lambda?

demos/levelOrderTraversal.tri

@@ -1,4 +1,5 @@
-!import "lib/base.tri" !Local
+!import "../lib/base.tri" Lib
+!import "../lib/list.tri" !Local
 
 main = exampleTwo
 -- Level Order Traversal of a labelled binary tree
@@ -17,15 +18,15 @@ main = exampleTwo
 --    /   /  \
 --   4   5    6
 
-label = \node : head node
+label = node : head node
 
-left = (\node : if (emptyList? node)
+left = node : (if (emptyList? node)
   []
   (if (emptyList? (tail node))
     []
     (head (tail node))))
 
-right = (\node : if (emptyList? node) 
+right = node : (if (emptyList? node)
   []
   (if (emptyList? (tail node))
     []
@@ -33,25 +34,25 @@ right = (\node : if (emptyList? node)
       []
       (head (tail (tail node))))))
 
-processLevel = y (\self queue : if (emptyList? queue) 
+processLevel = y (self queue : if (emptyList? queue)
   []
   (pair (map label queue) (self (filter
-    (\node : not? (emptyList? node)) 
+    (node : not? (emptyList? node))
       (append (map left queue) (map right queue))))))
 
-levelOrderTraversal_ = \a : processLevel (t a t)
+levelOrderTraversal_ = a : processLevel (t a t)
 
-toLineString = y (\self levels : if (emptyList? levels) 
+toLineString = y (self levels : if (emptyList? levels)
   ""
   (append
-    (append (map (\x : append x " ") (head levels)) "") 
+    (append (map (x : append x " ") (head levels)) "")
     (if (emptyList? (tail levels)) "" (append (t (t 10 t) t) (self (tail levels))))))
 
-levelOrderToString = \s : toLineString (levelOrderTraversal_ s)
+levelOrderToString = s : toLineString (levelOrderTraversal_ s)
 
-flatten = foldl (\acc x : append acc x) ""
+flatten = foldl (acc x : append acc x) ""
 
-levelOrderTraversal = \s : append (t 10 t) (flatten (levelOrderToString s))
+levelOrderTraversal = s : append (t 10 t) (flatten (levelOrderToString s))
 
 exampleOne = levelOrderTraversal [("1")
                                  [("2") [("4") t t] t]

demos/patternMatching.tri

@@ -0,0 +1,37 @@
+!import "../lib/patterns.tri" !Local
+
+-- We can do conditional pattern matching by providing a list of lists, where
+-- each sublist contains a boolean expression and a function to return if said
+-- boolean expression evaluates to true.
+
+value = 42
+main  = match value [[(equal? "Hello") (_ : ", world!")] [(equal? 42) (_ : "The answer.")]]
+
+-- < main
+-- > "The answer."
+
+matchExample = (x : match x
+  [[(equal? 1)  (_ : "one")]
+   [(equal? 2)  (_ : "two")]
+   [(equal? 3)  (_ : "three")]
+   [(equal? 4)  (_ : "four")]
+   [(equal? 5)  (_ : "five")]
+   [(equal? 6)  (_ : "six")]
+   [(equal? 7)  (_ : "seven")]
+   [(equal? 8)  (_ : "eight")]
+   [(equal? 9)  (_ : "nine")]
+   [(equal? 10) (_ : "ten")]
+   [ otherwise  (_ : "I ran out of fingers!")]])
+
+-- < matchExample 3
+-- > "three"
+-- < matchExample 5
+-- > "five"
+-- < matchExample 9
+-- > "nine"
+-- < matchExample 11
+-- > "I ran out of fingers!"
+-- < matchExample "three"
+-- > "I ran out of fingers!"
+-- < matchExample [("hello") ("world")]
+-- > "I ran out of fingers!"

demos/size.tri

@@ -1,12 +1,11 @@
-!import "lib/base.tri" !Local
+!import "../lib/base.tri" !Local
+!import "../lib/list.tri" !Local
 
 main = size size
 
-size = (\x :
+size = x : y (self x : compose succ (triage
-  (y (\self x :
+  id
-    compose succ
-      (triage
-        (\x : x)
   self
-        (\x y : compose (self x) (self y))
+  (x y : compose (self x) (self y))
-        x)) x 0))
+  x)
+) x 0

demos/toSource.tri

@@ -1,4 +1,5 @@
-!import "lib/base.tri" !Local
+!import "../lib/base.tri" !Local
+!import "../lib/list.tri" !Local
 
 main = toSource not?
 -- Thanks to intensionality, we can inspect the structure of a given value
@@ -17,25 +18,25 @@ main = toSource not?
 sourceLeaf = t (head "t")
 
 -- Stem case
-sourceStem = (\convert : (\a rest :
+sourceStem = convert : (a rest :
   t (head "(")                       -- Start with a left parenthesis "(".
     (t (head "t")                    -- Add a "t"
       (t (head " ")                  -- Add a space.
         (convert a                   -- Recursively convert the argument.
-          (t (head ")") rest))))))   -- Close with ")" and append the rest.
+          (t (head ")") rest)))))   -- Close with ")" and append the rest.
 
 -- Fork case
-sourceFork = (\convert : (\a b rest :
+sourceFork = convert : (a b rest :
   t (head "(")                           -- Start with a left parenthesis "(".
     (t (head "t")                        -- Add a "t"
       (t (head " ")                      -- Add a space.
         (convert a                       -- Recursively convert the first arg.
           (t (head " ")                  -- Add another space.
             (convert b                   -- Recursively convert the second arg.
-              (t (head ")") rest)))))))) -- Close with ")" and append the rest.
+              (t (head ")") rest))))))) -- Close with ")" and append the rest.
 
 -- Wrapper around triage 
-toSource_ = y (\self arg :
+toSource_ = y (self arg :
   triage
     sourceLeaf        -- `triage` "a" case, Leaf
     (sourceStem self) -- `triage` "b" case, Stem
@@ -43,7 +44,7 @@ toSource_ = y (\self arg :
     arg)              -- The term to be inspected
 
 -- toSource takes a single TC term and returns a String
-toSource = \v : toSource_ v ""
+toSource = v : toSource_ v ""
 
 exampleOne = toSource true -- OUT: "(t t)"
 exampleTwo = toSource not? -- OUT: "(t (t (t t) (t t t)) (t t (t t t)))"

flake.nix

@@ -34,6 +34,7 @@
         devShells.default = pkgs.mkShell {
           buildInputs = with pkgs; [
             haskellPackages.cabal-install
+            haskellPackages.ghc-events
             haskellPackages.ghcid
             customGHC
             upx

lib/base.tri

@@ -1,150 +1,74 @@
 false = t
 _     = t
 true  = t t
-k     = t t
+id    = a : a
-i     = t (t k) t
+const = a b : a
-s     = t (t (k t)) t
-m     = s i i
-b     = s (k s) k
-c     = s (s (k s) (s (k k) s)) (k k)
-id    = \a : a
 pair  = t
-if    = \cond then else : t (t else (t t then)) t cond
+if    = cond then else : t (t else (t t then)) t cond
 
-y = ((\mut wait fun : wait mut (\x : fun (wait mut x)))
+y = ((mut wait fun : wait mut (x : fun (wait mut x)))
-     (\x : x x)
+     (x : x x)
-     (\a0 a1 a2 : t (t a0) (t t a2) a1))
+     (a0 a1 a2 : t (t a0) (t t a2) a1))
 
-compose = \f g x : f (g x)
+compose = f g x : f (g x)
 
-triage = \leaf stem fork : t (t leaf stem) fork
+triage = leaf stem fork : t (t leaf stem) fork
-test   = triage "Leaf" (\_ : "Stem") (\_ _ : "Fork")
+test   = triage "Leaf" (_ : "Stem") (_ _ : "Fork")
 
-matchBool = (\ot of : triage
+matchBool = (ot of : triage
   of
-  (\_ : ot)
+  (_ : ot)
-  (\_ _ : ot)
+  (_ _ : ot)
 )
 
-matchList = \a b : triage a _ b
-
-matchPair = \a   : triage _ _ a
-
-not? = matchBool false true
-and? = matchBool id (\_ : false)
-emptyList? = matchList true (\_ _ : false)
-
-head = matchList t (\head _ : head)
-tail = matchList t (\_ tail : tail)
-
-or? = (\x y : 
-	matchBool 
-  	(matchBool (t t) (t t) y)
-  	(matchBool (t t) 0 y)
-  	x)
-xor? = matchBool id not?
-
-append = y (\self : matchList
-  (\k : k)
-  (\h r k : pair h (self r k)))
-
 lAnd = (triage
-  (\_     : false)
+  (_     : false)
-  (\_ x   : x)
+  (_ x   : x)
-  (\_ _ x : x))
+  (_ _ x : x))
 
 lOr = (triage
-  (\x     : x)
+  (x     : x)
-  (\_ _   : true)
+  (_ _   : true)
-  (\_ _ _ : true))
+  (_ _ _ : true))
 
-map_ = y (\self :
+matchPair = a : triage _ _ a
-  matchList
-    (\_ : t)
-    (\head tail f : pair (f head) (self tail f)))
-map = \f l : map_ l f
 
-equal? = y (\self : triage
+not? = matchBool false true
+and? = matchBool id (_ : false)
+
+or? = (x z : 
+  matchBool 
+    (matchBool true true z)
+    (matchBool true false z)
+    x)
+
+xor? = (x z : 
+  matchBool 
+    (matchBool false true z)
+    (matchBool true false z)
+    x)
+
+equal? = y (self : triage
   (triage
     true
-    (\_   : false)
+    (_   : false)
-    (\_ _ : false))
+    (_ _ : false))
-  (\ax :
+  (ax :
     triage
       false
       (self ax)
-      (\_ _ : false))
+      (_ _ : false))
-  (\ax ay :
+  (ax ay :
     triage
       false
-      (\_ : false)
+      (_ : false)
-      (\bx by : lAnd (self ax bx) (self ay by))))
+      (bx by : lAnd (self ax bx) (self ay by))))
 
-lExist? = y (\self x : matchList
+succ = y (self :
-  false
-  (\h z : or? (equal? x h) (self x z)))
-
-filter_ = y (\self : matchList
-  (\_ : t)
-  (\head tail f : matchBool (t head) i (f head) (self tail f)))
-filter  = \f l : filter_ l f
-
-foldl_ = y (\self f l x : matchList (\acc : acc) (\head tail acc : self f tail (f acc head)) l x)
-foldl  = \f x l : foldl_ f l x
-
-foldr_ = y (\self x f l : matchList x (\head tail : f (self x f tail) head) l)
-foldr  = \f x l : foldr_ x f l
-
-succ = y (\self :
   triage
     1
     t
     (triage
       (t (t t))
-      (\_ tail : t t (self tail))
+      (_ tail : t t (self tail))
       t))
-
-length = y (\self : matchList
-  0
-  (\_ tail : succ (self tail)))
-
-reverse = y (\self : matchList
-  t
-  (\head tail : append (self tail) (pair head t)))
-
-snoc = y (\self x : matchList
-  (pair x t)
-  (\h z : pair h (self x z)))
-
-count = y (\self x : matchList
-  0
-  (\h z : matchBool 
-    (succ (self x z))
-    (self x z)
-    (equal? x h)))
-
-last = y (\self : matchList
-  t
-  (\hd tl : matchBool
-    hd
-    (self tl)
-    (emptyList? tl)))
-
-all? = y (\self pred : matchList
-  true
-  (\h z : and? (pred h) (self pred z)))
-
-any? = y (\self pred : matchList
-  false
-  (\h z : or? (pred h) (self pred z)))
-
-unique_ = y (\self seen : matchList
-  t
-  (\head rest : matchBool
-    (self seen rest)
-    (pair head (self (pair head seen) rest))
-    (lExist? head seen)))
-unique = \xs : unique_ t xs
-
-intersect = \xs ys : filter (\x : lExist? x ys) xs
-union     = \xs ys : unique (append xs ys)

lib/list.tri

@@ -0,0 +1,70 @@
+!import "base.tri" !Local
+
+_ = t
+
+matchList = a b : triage a _ b
+
+emptyList? = matchList true (_ _ : false)
+head = matchList t (head _ : head)
+tail = matchList t (_ tail : tail)
+
+append = y (self : matchList
+  (k : k)
+  (h r k : pair h (self r k)))
+
+lExist? = y (self x : matchList
+  false
+  (h z : or? (equal? x h) (self x z)))
+
+map_ = y (self :
+  matchList
+    (_ : t)
+    (head tail f : pair (f head) (self tail f)))
+map = f l : map_ l f
+
+filter_ = y (self : matchList
+  (_ : t)
+  (head tail f : matchBool (t head) id (f head) (self tail f)))
+filter  = f l : filter_ l f
+
+foldl_ = y (self f l x : matchList (acc : acc) (head tail acc : self f tail (f acc head)) l x)
+foldl  = f x l : foldl_ f l x
+
+foldr_ = y (self x f l : matchList x (head tail : f (self x f tail) head) l)
+foldr  = f x l : foldr_ x f l
+
+length = y (self : matchList
+  0
+  (_ tail : succ (self tail)))
+
+reverse = y (self : matchList
+  t
+  (head tail : append (self tail) (pair head t)))
+
+snoc = y (self x : matchList
+  (pair x t)
+  (h z : pair h (self x z)))
+
+count = y (self x : matchList
+  0
+  (h z : matchBool
+    (succ (self x z))
+    (self x z)
+    (equal? x h)))
+
+last = y (self : matchList
+  t
+  (hd tl : matchBool
+    hd
+    (self tl)
+    (emptyList? tl)))
+
+all? = y (self pred : matchList
+  true
+  (h z : and? (pred h) (self pred z)))
+
+any? = y (self pred : matchList
+  false
+  (h z : or? (pred h) (self pred z)))
+
+intersect = xs ys : filter (x : lExist? x ys) xs

lib/patterns.tri

@@ -0,0 +1,24 @@
+!import "base.tri" !Local
+!import "list.tri" List
+
+match_ = y (self value patterns :
+  triage
+    t
+    (_ : t)
+    (pattern rest :
+      triage
+        t
+        (_ : t)
+        (test result :
+          if (test value)
+             (result value)
+             (self value rest))
+        pattern)
+    patterns)
+
+match = (value patterns :
+  match_ value (List.map (sublist :
+    pair (List.head sublist) (List.head (List.tail sublist)))
+    patterns))
+
+otherwise = const (t t)

src/Eval.hs

@@ -3,11 +3,30 @@ module Eval where
 import Parser
 import Research
 
-import Data.List (partition, (\\))
+import           Data.List   (partition, (\\), elemIndex)
 import           Data.Map    (Map)
+import           Data.Set    (Set)
+
+import qualified Data.Foldable as F
 import qualified Data.Map as Map
 import qualified Data.Set as Set
 
+data DB
+  = BVar Int          -- bound (0 = nearest binder)
+  | BFree String      -- free/global
+  | BLam DB
+  | BApp DB DB
+  | BLeaf
+  | BStem DB
+  | BFork DB DB
+  | BStr String
+  | BInt Integer
+  | BList [DB]
+  | BEmpty
+  deriving (Eq, Show)
+
+type Uses = [Bool]
+
 evalSingle :: Env -> TricuAST -> Env
 evalSingle env term
   | SDef name [] body <- term
@@ -62,56 +81,75 @@ evalAST env term
 elimLambda :: TricuAST -> TricuAST
 elimLambda = go
   where
-    -- η-reduction
+    go term
-    go (SLambda [v] (SApp f (SVar x)))
+      | etaReduction term   = go (etaReduceResult term)
-      | v == x && not (isFree v f) = elimLambda f
+      | triagePattern term  = _TRI
-    -- Triage optimization
+      | composePattern term = _B
-    go (SLambda [a] (SLambda [b] (SLambda [c] body)))
+      | lambdaList term     = go (lambdaListResult term)
-      | body == triageBody         = _TRIAGE
+      | nestedLambda term   = nestedLambdaResult term
+      | application term    = applicationResult term
+      | otherwise           = term
+
+    -- patterns (now DB-indexed where it matters)
+    etaReduction (SLambda [v] (SApp f (SVar x))) = v == x && not (usesBinder v f)
+    etaReduction _ = False
+
+    -- triage: \a b c -> TLeaf (TLeaf a b) c  (checked in DB with a↦2, b↦1, c↦0)
+    triagePattern (SLambda [a] (SLambda [b] (SLambda [c] body))) =
+      toDB [c,b,a] body == triageBodyDB
+    triagePattern _ = False
+
+    -- compose: \f g x -> f (g x)  (checked in DB with f↦2, g↦1, x↦0)
+    composePattern (SLambda [f] (SLambda [g] (SLambda [x] body))) =
+      toDB [x,g,f] body == composeBodyDB
+    composePattern _ = False
+
+    lambdaList (SLambda [_] (SList _)) = True
+    lambdaList _ = False
+
+    nestedLambda (SLambda (_:_) _) = True
+    nestedLambda _ = False
+
+    application (SApp _ _) = True
+    application _ = False
+
+    -- rewrites
+    etaReduceResult (SLambda [_] (SApp f _)) = f
+
+    lambdaListResult (SLambda [v] (SList xs)) =
+      SLambda [v] (foldr wrapTLeaf TLeaf xs)
       where
-        triageBody =
+        wrapTLeaf m r = SApp (SApp TLeaf m) r
-          SApp (SApp TLeaf (SApp (SApp TLeaf (SVar a)) (SVar b))) (SVar c)
-    -- Composition optimization
-    go (SLambda [f] (SLambda [g] (SLambda [x] body)))
-      | body == SApp (SVar f) (SApp (SVar g) (SVar x)) = _B
-    -- General elimination
-    go (SLambda (v:vs) body)
-      | null vs                    = toSKI v (elimLambda body)
-      | otherwise                  = elimLambda (SLambda [v] (SLambda vs body))
-    go (SApp f g)                  = SApp (elimLambda f) (elimLambda g)
-    go x                           = x
 
-    toSKI x (SVar y)
+    -- The key change: use DB bracket abstraction for the final parameter.
-      | x == y           = _I
+    nestedLambdaResult (SLambda (v:vs) body)
-      | otherwise        = SApp _K (SVar y)
+      | null vs   =
-    toSKI x t@(SApp n u)
+          let body' = go body
-      | not (isFree x t) = SApp _K t
+              db    = toDB [v] body'
-      | otherwise        = SApp (SApp _S (toSKI x n)) (toSKI x u)
+          in toSKIKiselyov db 
-    toSKI x t
+      | otherwise = go (SLambda [v] (SLambda vs body))
-      | not (isFree x t) = SApp _K t
-      | otherwise        = errorWithoutStackTrace "Unhandled toSKI conversion"
 
+    applicationResult (SApp f g) = SApp (go f) (go g)
+
+-- combinators and special forms (unchanged)
 _S   = parseSingle "t (t (t t t)) t"
 _K   = parseSingle "t t"
 _I   = parseSingle "t (t (t t)) t"
+_R   = parseSingle "(t (t (t t (t (t (t (t (t (t (t t (t (t (t t t)) t))) (t (t (t t (t t))) (t (t (t t t)) t)))) (t t (t t))))))) (t t))"
+_C   = parseSingle "(t (t (t (t (t t (t (t (t t t)) t))) (t (t (t t (t t))) (t (t (t t t)) t)))) (t t (t t)))"
 _B   = parseSingle "t (t (t t (t (t (t t t)) t))) (t t)"
-    _TRIAGE  = parseSingle "t (t (t t (t (t (t t t))))) t"
+_T   = SApp _C _I
+_TRI = parseSingle "t (t (t t (t (t (t t t))))) t"
+
+-- pattern bodies (kept for reference; checks are now DB-based)
+triageBody a b c   = SApp (SApp TLeaf (SApp (SApp TLeaf (SVar a)) (SVar b))) (SVar c)
+composeBody f g x  = SApp (SVar f) (SApp (SVar g) (SVar x))
 
 isFree :: String -> TricuAST -> Bool
-isFree x = Set.member x . freeVars
+isFree x t = Set.member x (freeVars t)
 
-freeVars :: TricuAST -> Set.Set String
+freeVars :: TricuAST -> Set String
-freeVars (SVar    v    ) = Set.singleton v
+freeVars = freeDBNames . toDB []
-freeVars (SInt    _    ) = Set.empty
-freeVars (SStr    _    ) = Set.empty
-freeVars (SList   s    ) = foldMap freeVars s
-freeVars (SApp    f a  ) = freeVars f <> freeVars a
-freeVars  TLeaf          = Set.empty
-freeVars (SDef   _ _ b)  = freeVars b
-freeVars (TStem   t    ) = freeVars t
-freeVars (TFork   l r  ) = freeVars l <> freeVars r
-freeVars (SLambda v b  ) = foldr Set.delete (freeVars b) v
-freeVars  _              = Set.empty
 
 reorderDefs :: Env -> [TricuAST] -> [TricuAST]
 reorderDefs env defs
@@ -128,7 +166,7 @@ reorderDefs env defs
     graph = buildDepGraph defsOnly
     sortedDefs = sortDeps graph
     defMap = Map.fromList [(name, def) | def@(SDef name _ _) <- defsOnly]
-    orderedDefs = map (\name -> defMap Map.! name) sortedDefs
+    orderedDefs = map (defMap Map.!) sortedDefs
 
     freeVarsDefs = foldMap snd defsWithFreeVars
     freeVarsOthers = foldMap freeVars others
@@ -136,23 +174,28 @@ reorderDefs env defs
     validNames = Set.fromList defNames `Set.union` Set.fromList (Map.keys env)
     missingDeps = Set.toList (allFreeVars `Set.difference` validNames)
 
-    isDef (SDef _ _ _) = True
+    isDef SDef {} = True
     isDef _       = False
 
 buildDepGraph :: [TricuAST] -> Map.Map String (Set.Set String)
 buildDepGraph topDefs
-  | not (null duplicateNames) =
+  | not (null conflictingDefs) =
       errorWithoutStackTrace $
-        "Duplicate definitions detected: " ++ show duplicateNames
+        "Conflicting definitions detected: " ++ show conflictingDefs
   | otherwise =
       Map.fromList
         [ (name, depends topDefs (SDef name [] body))
         | SDef name _ body <- topDefs]
   where
-    names = [name | SDef name _ _ <- topDefs]
+    defsMap = Map.fromListWith (++)
-    duplicateNames =
+      [(name, [(name, body)]) | SDef name _ body <- topDefs]
-      [ name | (name, count) <- Map.toList (countOccurrences names) , count > 1]
+
-    countOccurrences = foldr (\x -> Map.insertWith (+) x 1) Map.empty
+    conflictingDefs =
+      [ name
+      | (name, defs) <- Map.toList defsMap
+      , let bodies = map snd defs
+      , not $ all (== head bodies) (tail bodies)
+      ]
 
 sortDeps :: Map.Map String (Set.Set String) -> [String]
 sortDeps graph = go [] Set.empty (Map.keys graph)
@@ -187,3 +230,284 @@ mainResult :: Env -> T
 mainResult r = case Map.lookup "main" r of
   Just  a -> a
   Nothing -> errorWithoutStackTrace "No valid definition for `main` found."
+
+-- Convert named TricuAST to De Bruijn form
+toDB :: [String] -> TricuAST -> DB
+toDB env = \case
+  SVar v       -> maybe (BFree v) BVar (elemIndex v env)
+  SLambda vs b ->
+    let env' = reverse vs ++ env
+        body = toDB env' b
+    in foldr (\_ acc -> BLam acc) body vs
+  SApp f a     -> BApp (toDB env f) (toDB env a)
+  TLeaf        -> BLeaf
+  TStem t      -> BStem (toDB env t)
+  TFork l r    -> BFork (toDB env l) (toDB env r)
+  SStr s       -> BStr s
+  SInt n       -> BInt n
+  SList xs     -> BList (map (toDB env) xs)
+  SEmpty       -> BEmpty
+  SDef{}       -> error "toDB: unexpected SDef at this stage"
+  SImport _ _  -> BEmpty
+
+-- Does a term depend on the current binder (level 0)?
+dependsOnLevel :: Int -> DB -> Bool
+dependsOnLevel lvl = \case
+  BVar k      -> k == lvl
+  BLam t      -> dependsOnLevel (lvl + 1) t
+  BApp f a    -> dependsOnLevel lvl f || dependsOnLevel lvl a
+  BStem t     -> dependsOnLevel lvl t
+  BFork l r   -> dependsOnLevel lvl l || dependsOnLevel lvl r
+  BList xs    -> any (dependsOnLevel lvl) xs
+  _           -> False
+
+-- Collect free *global* names (i.e., unbound)
+freeDBNames :: DB -> Set String
+freeDBNames = \case
+  BFree s   -> Set.singleton s
+  BVar _    -> mempty
+  BLam t    -> freeDBNames t
+  BApp f a  -> freeDBNames f <> freeDBNames a
+  BLeaf     -> mempty
+  BStem t   -> freeDBNames t
+  BFork l r -> freeDBNames l <> freeDBNames r
+  BStr _    -> mempty
+  BInt _    -> mempty
+  BList xs  -> foldMap freeDBNames xs
+  BEmpty    -> mempty
+
+-- Helper: “is the binder named v used in body?”
+usesBinder :: String -> TricuAST -> Bool
+usesBinder v body = dependsOnLevel 0 (toDB [v] body)
+
+-- Expected DB bodies for the named special patterns (under env [a,b,c] -> indices 2,1,0)
+triageBodyDB :: DB
+triageBodyDB =
+  BApp (BApp BLeaf (BApp (BApp BLeaf (BVar 2)) (BVar 1))) (BVar 0)
+
+composeBodyDB :: DB
+composeBodyDB =
+  BApp (BVar 2) (BApp (BVar 1) (BVar 0))
+
+-- Convert DB -> TricuAST for subterms that contain NO binders (no BLam, no BVar)
+fromDBClosed :: DB -> TricuAST
+fromDBClosed = \case
+  BFree s   -> SVar s
+  BApp f a  -> SApp (fromDBClosed f) (fromDBClosed a)
+  BLeaf     -> TLeaf
+  BStem t   -> TStem (fromDBClosed t)
+  BFork l r -> TFork (fromDBClosed l) (fromDBClosed r)
+  BStr s    -> SStr s
+  BInt n    -> SInt n
+  BList xs  -> SList (map fromDBClosed xs)
+  BEmpty    -> SEmpty
+  -- Anything bound would be a logic error if we call this correctly.
+  BLam _    -> error "fromDBClosed: unexpected BLam"
+  BVar _    -> error "fromDBClosed: unexpected bound variable"
+
+-- DB-native bracket abstraction over the innermost binder (level 0).
+-- This mirrors your old toSKI, but is purely index-driven.
+toSKIDB :: DB -> TricuAST
+toSKIDB t
+  | not (dependsOnLevel 0 t) = SApp _K (fromDBClosed t)
+toSKIDB (BVar 0)             = _I
+toSKIDB (BApp n u)           = SApp (SApp _S (toSKIDB n)) (toSKIDB u)
+toSKIDB (BList xs) =
+  let anyUses = any (dependsOnLevel 0) xs
+  in if not anyUses
+        then SApp _K (SList (map fromDBClosed xs))
+        else SList (map toSKIDB xs)
+toSKIDB other =
+  errorWithoutStackTrace $ "Unhandled toSKI(DB) conversion: " ++ show other
+
+app2 :: TricuAST -> TricuAST -> TricuAST
+app2 f x = SApp f x
+
+app3 :: TricuAST -> TricuAST -> TricuAST -> TricuAST
+app3 f x y = SApp (SApp f x) y
+
+-- Core converter that *does not* perform the λ-step; it just returns (Γ, d).
+-- Supported shapes: variables, applications, closed literals (Leaf/Int/Str/Empty),
+-- closed lists. For anything where the binder occurs under structural nodes
+-- (Stem/Fork/List-with-use), we deliberately bail so the caller can fall back.
+kisConv :: DB -> Either String (Uses, TricuAST)
+kisConv = \case
+  BVar 0     -> Right ([True], _I)
+  BVar n | n > 0 -> do
+    (g,d) <- kisConv (BVar (n - 1))
+    Right (False:g, d)
+  BApp e1 e2 -> do
+    (g1,d1) <- kisConv e1
+    (g2,d2) <- kisConv e2
+    let g = zipWithDefault False (||) g1 g2   -- <— propagate Γ outside (#)
+        d = kisHash (g1,d1) (g2,d2)           -- <— (#) yields only the term
+    Right (g, d)
+  -- Treat closed constants as free 'combinator leaves' (no binder use).
+  BLeaf      -> Right ([], TLeaf)
+  BStr s     -> Right ([], SStr s)
+  BInt n     -> Right ([], SInt n)
+  BEmpty     -> Right ([], SEmpty)
+  -- Closed list: allowed. If binder is used anywhere, we punt to fallback.
+  BList xs
+    | any (dependsOnLevel 0) xs -> Left "List with binder use: fallback"
+    | otherwise                 -> Right ([], SList (map fromDBClosed xs))
+  -- For structural nodes, only allow if *closed* wrt the binder.
+  BStem t
+    | dependsOnLevel 0 t -> Left "Stem with binder use: fallback"
+    | otherwise          -> Right ([], TStem (fromDBClosed t))
+  BFork l r
+    | dependsOnLevel 0 l || dependsOnLevel 0 r -> Left "Fork with binder use: fallback"
+    | otherwise                                -> Right ([], TFork (fromDBClosed l) (fromDBClosed r))
+  -- We shouldn’t see BLam under elim; treat as unsupported so we fallback.
+  BLam _      -> Left "Nested lambda under body: fallback"
+  BFree s     -> Right ([], SVar s)
+
+-- Application combiner with K-optimization (lazy weakening).
+-- Mirrors Lynn’s 'optK' rules: choose among S, B, C, R based on leading flags.
+-- η-aware (#) with K-optimization (adapted from TS kiselyov_eta)
+kisHash :: (Uses, TricuAST) -> (Uses, TricuAST) -> TricuAST
+kisHash (g1, d1) (g2, d2) =
+  case g1 of
+    [] -> case g2 of
+      []            -> SApp d1 d2
+      True:gs2      -> if isId2 (g2, d2)
+                         then d1
+                         else kisHash ([], SApp _B d1) (gs2, d2)
+      False:gs2     -> kisHash ([], d1) (gs2, d2)
+
+    True:gs1 -> case g2 of
+      []            -> if isId2 (g1, d1)
+                         then SApp _T d2
+                         else kisHash ([], SApp _R d2) (gs1, d1)
+      _ ->
+        if isId2 (g1, d1) && case g2 of { False:_ -> True; _ -> False }
+          then kisHash ([], _T) (tail g2, d2)
+        else
+          -- NEW: coalesce the longest run of identical head pairs and apply bulk op once
+          let ((h1, h2), count) = headPairRun g1 g2
+              g1' = drop count g1
+              g2' = drop count g2
+          in case (h1, h2) of
+               (False, False) ->
+                 kisHash (g1', d1) (g2', d2)
+               (False, True)  ->
+                 let d1' = kisHash ([], bulkB count) (g1', d1)
+                 in  kisHash (g1', d1') (g2', d2)
+               (True, False)  ->
+                 let d1' = kisHash ([], bulkC count) (g1', d1)
+                 in  kisHash (g1', d1') (g2', d2)
+               (True, True)   ->
+                 let d1' = kisHash ([], bulkS count) (g1', d1)
+                 in  kisHash (g1', d1') (g2', d2)
+
+    False:gs1 -> case g2 of
+      []            -> kisHash (gs1, d1) ([], d2)
+      _             ->
+        if isId2 (g1, d1) && case g2 of { False:_ -> True; _ -> False }
+          then kisHash ([], _T) (tail g2, d2)
+        else case g2 of
+          True:gs2   ->
+            let d1' = kisHash ([], _B) (gs1, d1)
+            in  kisHash (gs1, d1') (gs2, d2)
+          False:gs2  ->
+            kisHash (gs1, d1) (gs2, d2)
+  where
+    tail (_:xs) = xs
+    tail []     = []
+
+
+toSKIKiselyov :: DB -> TricuAST
+toSKIKiselyov body =
+  case kisConv body of
+    Right ([], d)          -> SApp _K d
+    Right (True:_ , d)     -> d
+    Right (False:g, d)     -> kisHash ([], _K) (g, d)  -- no snd
+    Left _                 -> starSKIBCOpEtaDB body   -- was: toSKIDB body
+
+zipWithDefault :: a -> (a -> a -> a) -> [a] -> [a] -> [a]
+zipWithDefault d f []     ys     = map (f d) ys
+zipWithDefault d f xs     []     = map (\x -> f x d) xs
+zipWithDefault d f (x:xs) (y:ys) = f x y : zipWithDefault d f xs ys
+
+isNode :: TricuAST -> Bool
+isNode t = case t of
+  TLeaf -> True
+  _     -> False
+
+isApp2 :: TricuAST -> Maybe (TricuAST, TricuAST)
+isApp2 (SApp a b) = Just (a, b)
+isApp2 _          = Nothing
+
+isKop :: TricuAST -> Bool
+isKop t = case isApp2 t of
+  Just (a,b) -> isNode a && isNode b
+  _          -> False
+
+-- detects the two canonical I-shapes in the tree calculus:
+--   △ (△ (△ △)) x    OR    △ (△ △ △) △
+isId :: TricuAST -> Bool
+isId t = case isApp2 t of
+  Just (ab, c) -> case isApp2 ab of
+    Just (a, b) | isNode a ->
+      case isApp2 b of
+        Just (b1, b2) ->
+          (isNode b1 && isKop b2) ||
+          (isKop b1 && isNode b2 && isNode c)
+        _ -> False
+    _ -> False
+  _ -> False
+
+-- head-True only, tail empty, and term is identity
+isId2 :: (Uses, TricuAST) -> Bool
+isId2 (True:[], t) = isId t
+isId2 _            = False
+
+-- Bulk helpers built from SKI (no new primitives)
+bPrime :: TricuAST
+bPrime = SApp _B _B                            -- B' = B B
+
+cPrime :: TricuAST
+cPrime = SApp (SApp _B (SApp _B _C)) _B        -- C' = B (B C) B
+
+sPrime :: TricuAST
+sPrime = SApp (SApp _B (SApp _B _S)) _B        -- S' = B (B S) B
+
+bulkB :: Int -> TricuAST
+bulkB n | n <= 1    = _B
+        | otherwise = SApp bPrime (bulkB (n - 1))
+
+bulkC :: Int -> TricuAST
+bulkC n | n <= 1    = _C
+        | otherwise = SApp cPrime (bulkC (n - 1))
+
+bulkS :: Int -> TricuAST
+bulkS n | n <= 1    = _S
+        | otherwise = SApp sPrime (bulkS (n - 1))
+
+-- Count how many leading pairs (a,b) repeat at the head of zip g1 g2
+headPairRun :: [Bool] -> [Bool] -> ((Bool, Bool), Int)
+headPairRun g1 g2 =
+  case zip g1 g2 of
+    []       -> ((False, False), 0)
+    (h:rest) -> (h, 1 + length (takeWhile (== h) rest))
+
+-- DB-native star_skibc_op_eta (adapted from strategies.mts), binder = level 0
+starSKIBCOpEtaDB :: DB -> TricuAST
+starSKIBCOpEtaDB t
+  | not (dependsOnLevel 0 t) = SApp _K (fromDBClosed t)
+starSKIBCOpEtaDB (BVar 0)     = _I
+starSKIBCOpEtaDB (BApp e1 e2)
+  -- if binder not in right: use C
+  | not (dependsOnLevel 0 e2)
+  = SApp (SApp _C (starSKIBCOpEtaDB e1)) (fromDBClosed e2)
+  -- if binder not in left:
+  | not (dependsOnLevel 0 e1)
+  = case e2 of
+      -- η case: \x. f x  ==>  f
+      BVar 0 -> fromDBClosed e1
+      _      -> SApp (SApp _B (fromDBClosed e1)) (starSKIBCOpEtaDB e2)
+  -- otherwise: S
+  | otherwise
+  = SApp (SApp _S (starSKIBCOpEtaDB e1)) (starSKIBCOpEtaDB e2)
+-- Structural nodes with binder underneath: fall back to plain SKI (rare)
+starSKIBCOpEtaDB other        = toSKIDB other

src/FileEval.hs

@@ -6,12 +6,34 @@ import Parser
 import Research
 
 import Data.List       (partition)
+import Data.Maybe      (mapMaybe)
 import Control.Monad   (foldM)
 import System.IO
+import System.FilePath (takeDirectory, normalise, (</>))
 
 import qualified Data.Map as Map
 import qualified Data.Set as Set
 
+extractMain :: Env -> Either String T
+extractMain env =
+  case Map.lookup "main" env of
+    Just result -> Right result
+    Nothing -> Left "No `main` function detected"
+
+processImports :: Set.Set FilePath -> FilePath -> FilePath -> [TricuAST]
+                 -> Either String ([TricuAST], [(FilePath, String, FilePath)])
+processImports seen base currentPath asts =
+  let (imports, nonImports) = partition isImp asts
+      importPaths = mapMaybe getImportInfo imports
+  in if currentPath `Set.member` seen
+     then Left $ "Encountered cyclic import: " ++ currentPath
+     else Right (nonImports, importPaths)
+  where
+    isImp (SImport _ _) = True
+    isImp _ = False
+    getImportInfo (SImport p n) = Just (p, n, makeRelativeTo currentPath p)
+    getImportInfo _ = Nothing
+
 evaluateFileResult :: FilePath -> IO T
 evaluateFileResult filePath = do
   contents <- readFile filePath
@@ -19,11 +41,11 @@ evaluateFileResult filePath = do
   case parseProgram tokens of
     Left err -> errorWithoutStackTrace (handleParseError err)
     Right ast -> do
-      ast <- preprocessFile filePath
+      processedAst <- preprocessFile filePath
-      let finalEnv = evalTricu Map.empty ast
+      let finalEnv = evalTricu Map.empty processedAst
-      case Map.lookup "main" finalEnv of
+      case extractMain finalEnv of
-        Just finalResult -> return finalResult
+        Right result -> return result
-        Nothing -> errorWithoutStackTrace "No `main` function detected"
+        Left err -> errorWithoutStackTrace err
 
 evaluateFile :: FilePath -> IO Env
 evaluateFile filePath = do
@@ -46,38 +68,33 @@ evaluateFileWithContext env filePath = do
       pure $ evalTricu env ast
 
 preprocessFile :: FilePath -> IO [TricuAST]
-preprocessFile = preprocessFile' Set.empty
+preprocessFile p = preprocessFile' Set.empty p p
 
-preprocessFile' :: Set.Set FilePath -> FilePath -> IO [TricuAST]
+preprocessFile' :: Set.Set FilePath -> FilePath -> FilePath -> IO [TricuAST]
-preprocessFile' inProgress filePath
+preprocessFile' seen base currentPath = do
-  | filePath `Set.member` inProgress = 
+  contents <- readFile currentPath
-      errorWithoutStackTrace $ "Encountered cyclic import: " ++ filePath
-  | otherwise = do
-      contents <- readFile filePath
   let tokens = lexTricu contents
   case parseProgram tokens of
     Left err -> errorWithoutStackTrace (handleParseError err)
-        Right asts -> do
+    Right ast ->
-          let (imports, nonImports) = partition isImport asts
+      case processImports seen base currentPath ast of
-          let newInProgress = Set.insert filePath inProgress
+        Left err -> errorWithoutStackTrace err
-          importedASTs <- concat <$> 
+        Right (nonImports, importPaths) -> do
-            mapM (processImport newInProgress "") imports
+          let seen' = Set.insert currentPath seen
-          pure $ importedASTs ++ nonImports
+          imported <- concat <$> mapM (processImportPath seen' base) importPaths
+          pure $ imported ++ nonImports
   where
-    isImport :: TricuAST -> Bool
+    processImportPath seen base (path, name, importPath) = do
-    isImport (SImport _ _) = True
+      ast <- preprocessFile' seen base importPath
-    isImport _             = False
+      pure $ map (nsDefinition (if name == "!Local" then "" else name))
+           $ filter (not . isImp) ast
+    isImp (SImport _ _) = True
+    isImp _ = False
 
-    processImport :: Set.Set FilePath -> String -> TricuAST -> IO [TricuAST]
+makeRelativeTo :: FilePath -> FilePath -> FilePath
-    processImport prog currentModule (SImport path "!Local") = do
+makeRelativeTo f i =
-      ast <- preprocessFile' prog path
+    let d = takeDirectory f
-      let defs = filter (not . isImport) ast
+    in normalise $ d </> i
-      pure $ map (nsDefinition currentModule) defs
-    processImport prog _ (SImport path name) = do
-      ast <- preprocessFile' prog path
-      let defs = filter (not . isImport) ast
-      pure $ map (nsDefinition name) defs
-    processImport _ _ _ = error "Unexpected non-import in processImport"
 
 nsDefinitions :: String -> [TricuAST] -> [TricuAST]
 nsDefinitions moduleName = map (nsDefinition moduleName)

src/Lexer.hs

@@ -3,6 +3,7 @@ module Lexer where
 import Research
 
 import Control.Monad               (void)
+import Data.Functor                (($>))
 import Data.Void
 import Text.Megaparsec
 import Text.Megaparsec.Char hiding (space)
@@ -40,7 +41,6 @@ tricuLexer = do
       , try stringLiteral
       , assign
       , colon
-      , backslash
       , openParen
       , closeParen
       , openBracket
@@ -54,7 +54,7 @@ lexTricu input = case runParser tricuLexer "" input of
 
 
 keywordT :: Lexer LToken
-keywordT = string "t" *> notFollowedBy alphaNumChar *> pure LKeywordT
+keywordT = string "t" *> notFollowedBy alphaNumChar $> LKeywordT
 
 identifier :: Lexer LToken
 identifier = do
@@ -63,7 +63,7 @@ identifier = do
               <|> digitChar <|> char '_' <|> char '-' <|> char '?'
               <|> char '$'  <|> char '#' <|> char '@' <|> char '%'
   let name = first : rest
-  if (name == "t" || name == "!result")
+  if name == "t" || name == "!result"
     then fail "Keywords (`t`, `!result`) cannot be used as an identifier"
     else return (LIdentifier name)
 
@@ -76,7 +76,7 @@ namespace = do
   return (LNamespace name)
 
 dot :: Lexer LToken
-dot = char '.' *> pure LDot
+dot = char '.' $> LDot
 
 lImport :: Lexer LToken
 lImport = do
@@ -88,28 +88,25 @@ lImport = do
   return (LImport path name)
 
 assign :: Lexer LToken
-assign = char '=' *> pure LAssign
+assign = char '=' $> LAssign
 
 colon :: Lexer LToken
-colon = char ':' *> pure LColon
+colon = char ':' $> LColon
-
-backslash :: Lexer LToken
-backslash = char '\\' *> pure LBackslash
 
 openParen :: Lexer LToken
-openParen = char '(' *> pure LOpenParen
+openParen = char '(' $> LOpenParen
 
 closeParen :: Lexer LToken
-closeParen = char ')' *> pure LCloseParen
+closeParen = char ')' $> LCloseParen
 
 openBracket :: Lexer LToken
-openBracket = char '[' *> pure LOpenBracket
+openBracket = char '[' $> LOpenBracket
 
 closeBracket :: Lexer LToken
-closeBracket = char ']' *> pure LCloseBracket
+closeBracket = char ']' $> LCloseBracket
 
 lnewline :: Lexer LToken
-lnewline = char '\n' *> pure LNewline
+lnewline = char '\n' $> LNewline
 
 sc :: Lexer ()
 sc = space
@@ -125,7 +122,22 @@ integerLiteral = do
 stringLiteral :: Lexer LToken
 stringLiteral = do
   char '"'
-  content <- many (noneOf ['"'])
+  content <- manyTill Lexer.charLiteral (char '"')
-  char '"' --"
   return (LStringLiteral content)
 
+charLiteral :: Lexer Char
+charLiteral = escapedChar <|> normalChar
+  where
+    normalChar = noneOf ['"', '\\']
+    escapedChar = do
+      void $ char '\\'
+      c <- oneOf ['n', 't', 'r', 'f', 'b', '\\', '"', '\'']
+      return $ case c of
+        'n'  -> '\n'
+        't'  -> '\t'
+        'r'  -> '\r'
+        'f'  -> '\f'
+        'b'  -> '\b'
+        '\\' -> '\\'
+        '"'  -> '"'
+        '\'' -> '\''

src/Main.hs

@@ -63,18 +63,17 @@ main = do
   case args of
     Repl -> do
       putStrLn "Welcome to the tricu REPL"
-      putStrLn "You can exit with `CTRL+D` or the `!exit` command.`"
+      putStrLn "You may exit with `CTRL+D` or the `!exit` command."
+      putStrLn "Try typing `!` with tab completion for more commands."
       repl Map.empty
     Evaluate { file = filePaths, form = form } -> do
       result <- case filePaths of
-        [] -> do
+        [] -> runTricuT <$> getContents
-          t <- getContents
-          pure $ runTricu t
         (filePath:restFilePaths) -> do
             initialEnv <- evaluateFile filePath
             finalEnv <- foldM evaluateFileWithContext initialEnv restFilePaths
             pure $ mainResult finalEnv
-      let fRes = formatResult form result
+      let fRes = formatT form result
       putStr fRes
     TDecode { file = filePaths } -> do
       value <- case filePaths of
@@ -82,8 +81,48 @@ main = do
         (filePath:_) -> readFile filePath
       putStrLn $ decodeResult $ result $ evalTricu Map.empty $ parseTricu value
 
-runTricu :: String -> T
+-- Simple interfaces
-runTricu input =
+
+runTricu :: String -> String
+runTricu = formatT TreeCalculus . runTricuT
+
+runTricuT :: String -> T
+runTricuT input =
   let asts     = parseTricu input
       finalEnv = evalTricu Map.empty asts
    in result finalEnv
+
+runTricuEnv :: Env -> String -> String
+runTricuEnv env = formatT TreeCalculus . runTricuTEnv env
+
+runTricuTEnv :: Env -> String -> T
+runTricuTEnv env input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu env asts
+   in result finalEnv
+
+runTricuWithEnvT :: String -> (Env, T)
+runTricuWithEnvT input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu Map.empty asts
+   in (finalEnv, result finalEnv)
+
+runTricuWithEnv :: String -> (Env, String)
+runTricuWithEnv input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu Map.empty asts
+      res      = result finalEnv
+   in (finalEnv, formatT TreeCalculus res)
+
+runTricuEnvWithEnvT :: Env -> String -> (Env, T)
+runTricuEnvWithEnvT env input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu env asts
+   in (finalEnv, result finalEnv)
+
+runTricuEnvWithEnv :: Env -> String -> (Env, String)
+runTricuEnvWithEnv env input =
+  let asts     = parseTricu input
+      finalEnv = evalTricu env asts
+      res      = result finalEnv
+   in (finalEnv, formatT TreeCalculus res)

src/Parser.hs

@@ -130,7 +130,6 @@ parseFunctionM = do
 parseLambdaM :: ParserM TricuAST
 parseLambdaM = do
   let ident = (\case LIdentifier _ -> True; _ -> False)
-  _      <- satisfyM (== LBackslash)
   params <- some (satisfyM ident)
   _      <- satisfyM (== LColon)
   scnParserM
@@ -145,11 +144,11 @@ parseLambdaExpressionM = choice
 
 parseAtomicLambdaM :: ParserM TricuAST
 parseAtomicLambdaM = choice
-  [ parseVarM
+  [ try parseLambdaM
+  , parseVarM
   , parseTreeLeafM
   , parseLiteralM
   , parseListLiteralM
-  , try parseLambdaM
   , between (satisfyM (== LOpenParen)) (satisfyM (== LCloseParen)) parseLambdaExpressionM
   ]
 
@@ -205,7 +204,8 @@ parseTreeLeafOrParenthesizedM = choice
 
 parseAtomicM :: ParserM TricuAST
 parseAtomicM = choice
-  [ parseVarM
+  [ try parseLambdaM
+  , parseVarM
   , parseTreeLeafM
   , parseListLiteralM
   , parseGroupedM

src/REPL.hs

@@ -6,68 +6,153 @@ import Lexer
 import Parser
 import Research
 
-import Control.Exception      (SomeException, catch)
+import Control.Exception         (IOException, SomeException, catch
-import Control.Monad.IO.Class (liftIO)
+                                 , displayException)
+import Control.Monad             (forM_)
 import Control.Monad.Catch       (handle, MonadCatch)
-import Data.Char              (isSpace)
+import Control.Monad.IO.Class    (liftIO)
-import Data.List              ( dropWhile
+import Control.Monad.Trans.Class (lift)
-                              , dropWhileEnd
+import Control.Monad.Trans.Maybe (MaybeT(..), runMaybeT)
-                              , intercalate
+import Data.Char                 (isSpace, isUpper)
-                              , isPrefixOf)
+import Data.List                 (dropWhile, dropWhileEnd, isPrefixOf)
+import Data.Version (showVersion)
+import Paths_tricu (version)
 import System.Console.Haskeline
 
 import qualified Data.Map as Map
+import qualified Data.Text as T
+import qualified Data.Text.IO as T
 
 repl :: Env -> IO ()
-repl env = runInputT defaultSettings (withInterrupt (loop env True))
+repl env = runInputT settings (withInterrupt (loop env Decode))
   where
-    loop :: Env -> Bool -> InputT IO ()
+    settings :: Settings IO
-    loop env decode = handle (interruptHandler env decode) $ do
+    settings = Settings
+      { complete = completeWord Nothing " \t" completeCommands
+      , historyFile = Just "~/.local/state/tricu/history"
+      , autoAddHistory = True
+      }
+
+    completeCommands :: String -> IO [Completion]
+    completeCommands str = return $ map simpleCompletion $
+      filter (str `isPrefixOf`) commands
+      where
+        commands = [ "!exit"
+                   , "!output"
+                   , "!definitions"
+                   , "!import"
+                   , "!clear"
+                   , "!save"
+                   , "!reset"
+                   , "!version"
+                   ]
+
+    loop :: Env -> EvaluatedForm -> InputT IO ()
+    loop env form = handle (interruptHandler env form) $ do
       minput <- getInputLine "tricu < "
       case minput of
         Nothing -> outputStrLn "Exiting tricu"
         Just s
-          | strip s == "" -> loop env decode
+          | strip s == "" -> loop env form
           | strip s == "!exit" -> outputStrLn "Exiting tricu"
-          | strip s == "!decode" -> do
+          | strip s == "!clear" -> do
-              outputStrLn $ "Decoding " ++ (if decode then "disabled" else "enabled")
+              liftIO $ putStr "\ESC[2J\ESC[H"
-              loop env (not decode)
+              loop env form
-          | "!import" `isPrefixOf` strip s -> do
+          | strip s == "!reset" -> do
-              let afterImport = dropWhile (== ' ') $ drop (length ("!import" :: String)) (strip s)
+              outputStrLn "Environment reset to initial state"
-              if not (null afterImport)
+              loop Map.empty form
-                then outputStrLn "Warning: REPL imports are interactive; \
+          | strip s == "!version" -> do
-                                  \additional arguments are ignored."
+              outputStrLn $ "tricu version " ++ showVersion version
-                else pure ()
+              loop env form
-              path <- getInputLine "File path to load < "
+          | "!save" `isPrefixOf` strip s -> handleSave env form
-              case path of
+          | strip s == "!output" -> handleOutput env form
-                Nothing -> do
+          | strip s == "!definitions" -> do
-                  outputStrLn "No input received; stopping import."
+              let defs = Map.keys $ Map.delete "!result" env
-                  loop env decode
+              if null defs
-                Just p -> do
+                then outputStrLn "No definitions discovered."
-                  loadedEnv <- liftIO $ evaluateFileWithContext env
+                else do
-                    (strip p) `catch` \e -> errorHandler env e
+                  outputStrLn "Available definitions:"
-                  loop (Map.delete "!result" (Map.union loadedEnv env)) decode
+                  mapM_ outputStrLn defs
-          | take 2 s == "--" -> loop env decode
+              loop env form
+          | "!import" `isPrefixOf` strip s -> handleImport env form
+          | take 2 s == "--" -> loop env form
           | otherwise -> do
-              newEnv <- liftIO $ processInput env s decode `catch` errorHandler env
+              newEnv <- liftIO $ processInput env s form `catch` errorHandler env
-              loop newEnv decode
+              loop newEnv form
 
-    interruptHandler :: Env -> Bool -> Interrupt -> InputT IO ()
+    handleOutput :: Env -> EvaluatedForm -> InputT IO ()
-    interruptHandler env decode _ = do
+    handleOutput env currentForm = do
+      let formats = [Decode, TreeCalculus, FSL, AST, Ternary, Ascii]
+      outputStrLn "Available output formats:"
+      mapM_ (\(i, f) -> outputStrLn $ show i ++ ". " ++ show f)
+        (zip [1..] formats)
+
+      result <- runMaybeT $ do
+        input <- MaybeT $ getInputLine "Select output format (1-6) < "
+        case reads input of
+          [(n, "")] | n >= 1 && n <= 6 ->
+            return $ formats !! (n-1)
+          _ -> MaybeT $ return Nothing
+
+      case result of
+        Nothing -> do
+          outputStrLn "Invalid selection. Keeping current output format."
+          loop env currentForm
+        Just newForm -> do
+          outputStrLn $ "Output format changed to: " ++ show newForm
+          loop env newForm
+
+    handleImport :: Env -> EvaluatedForm -> InputT IO ()
+    handleImport env form = do
+      res <- runMaybeT $ do
+        let fset = setComplete completeFilename defaultSettings
+        path <- MaybeT $ runInputT fset $
+          getInputLineWithInitial "File path to load < " ("", "")
+
+        text <- MaybeT $ liftIO $ handle (\e -> do
+            putStrLn $ "Error reading file: " ++ displayException (e :: IOException)
+            return Nothing
+          ) $ Just <$> readFile (strip path)
+
+        case parseProgram (lexTricu text) of
+          Left err -> do
+            lift $ outputStrLn $ "Parse error: " ++ handleParseError err
+            MaybeT $ return Nothing
+          Right ast -> do
+            ns <- MaybeT $ runInputT defaultSettings $
+              getInputLineWithInitial "Namespace (or !Local for no namespace) < " ("", "")
+
+            let name = strip ns
+            if (name /= "!Local" && (null name || not (isUpper (head name)))) then do
+                lift $ outputStrLn "Namespace must start with an uppercase letter"
+                MaybeT $ return Nothing
+            else do
+                prog <- liftIO $ preprocessFile (strip path)
+                let code = case name of
+                      "!Local" -> prog
+                      _ -> nsDefinitions name prog
+                    env' = evalTricu env code
+                return env'
+      case res of
+        Nothing -> do
+          outputStrLn "Import cancelled"
+          loop env form
+        Just env' ->
+          loop (Map.delete "!result" env') form
+
+    interruptHandler :: Env -> EvaluatedForm -> Interrupt -> InputT IO ()
+    interruptHandler env form _ = do
       outputStrLn "Interrupted with CTRL+C\n\
                   \You can use the !exit command or CTRL+D to exit"
-      loop env decode
+      loop env form
 
-    processInput :: Env -> String -> Bool -> IO Env
+    processInput :: Env -> String -> EvaluatedForm -> IO Env
-    processInput env input decode = do
+    processInput env input form = do
       let asts   = parseTricu input
           newEnv = evalTricu env asts
       case Map.lookup "!result" newEnv of
         Just r -> do
-          putStrLn $ "tricu > " ++ 
+          putStrLn $ "tricu > " ++ formatT form r
-            if decode 
-              then decodeResult r
-              else show r
         Nothing -> pure ()
       return newEnv
 
@@ -78,3 +163,28 @@ repl env = runInputT defaultSettings (withInterrupt (loop env True))
 
     strip :: String -> String
     strip = dropWhileEnd isSpace . dropWhile isSpace
+
+    handleSave :: Env -> EvaluatedForm -> InputT IO ()
+    handleSave env form = do
+      let fset = setComplete completeFilename defaultSettings
+      path <- runInputT fset $
+        getInputLineWithInitial "File to save < " ("", "")
+
+      case path of
+        Nothing -> do
+          outputStrLn "Save cancelled"
+          loop env form
+        Just p -> do
+          let definitions = Map.toList $ Map.delete "!result" env
+              filepath = strip p
+
+          outputStrLn "Starting save..."
+          liftIO $ writeFile filepath ""
+          outputStrLn "File created..."
+          forM_ definitions $ \(name, value) -> do
+            let content = name ++ " = " ++ formatT TreeCalculus value ++ "\n"
+            outputStrLn $ "Writing definition: " ++ name ++ " with length " ++ show (length content)
+            liftIO $ appendFile filepath content
+          outputStrLn $ "Saved " ++ show (length definitions) ++ " definitions to " ++ p
+
+          loop env form

src/Research.hs

@@ -1,6 +1,5 @@
 module Research where
 
-import Control.Monad.State
 import Data.List                 (intercalate)
 import Data.Map                  (Map)
 import Data.Text                 (Text, replace)
@@ -16,7 +15,7 @@ data T = Leaf | Stem T | Fork T T
 -- Abstract Syntax Tree for tricu
 data TricuAST
   = SVar String
-  | SInt Int
+  | SInt Integer
   | SStr String
   | SList [TricuAST]
   | SDef String [String] TricuAST
@@ -34,12 +33,11 @@ data LToken
   = LKeywordT
   | LIdentifier String
   | LNamespace String
-  | LIntegerLiteral Int
+  | LIntegerLiteral Integer
   | LStringLiteral String
   | LAssign
   | LColon
   | LDot
-  | LBackslash
   | LOpenParen
   | LCloseParen
   | LOpenBracket
@@ -55,15 +53,24 @@ data EvaluatedForm = TreeCalculus | FSL | AST | Ternary | Ascii | Decode
 -- Environment containing previously evaluated TC terms
 type Env = Map.Map String T
 
--- Tree Calculus Reduction
+-- Tree Calculus Reduction Rules
+{- 
+  The t operator is left associative.
+  1.  t  t      a b       -> a
+  2.  t (t a)   b c       -> a c (b c)
+  3a. t (t a b) c t       -> a
+  3b. t (t a b) c (t u)   -> b u
+  3c. t (t a b) c (t u v) -> c u v
+-}
 apply :: T -> T -> T
+apply (Fork Leaf a)         _         = a
+apply (Fork (Stem a) b) c             = apply (apply a c) (apply b c)
+apply (Fork (Fork a  b) c)  Leaf      = a
+apply (Fork (Fork a  b) c) (Stem u)   = apply b u
+apply (Fork (Fork a  b) c) (Fork u v) = apply (apply c u) v
+-- Left associative `t`
 apply  Leaf b                         = Stem b
 apply (Stem a) b                      = Fork a b
-apply (Fork Leaf a) _                   = a
-apply (Fork (Stem a1) a2) b             = apply (apply a1 b) (apply a2 b)
-apply (Fork (Fork a1 a2) a3) Leaf       = a1
-apply (Fork (Fork a1 a2) a3) (Stem u)   = apply a2 u
-apply (Fork (Fork a1 a2) a3) (Fork u v) = apply (apply a3 u) v
 
 -- Booleans
 _false :: T
@@ -77,9 +84,9 @@ _not = Fork (Fork _true (Fork Leaf _false)) Leaf
 
 -- Marshalling
 ofString :: String -> T
-ofString str = ofList (map ofNumber (map fromEnum str))
+ofString str = ofList $ map (ofNumber . toInteger . fromEnum) str
 
-ofNumber :: Int -> T
+ofNumber :: Integer -> T
 ofNumber 0 = Leaf
 ofNumber n =
   Fork
@@ -87,10 +94,9 @@ ofNumber n =
     (ofNumber (n `div` 2))
 
 ofList :: [T] -> T
-ofList [] = Leaf
+ofList = foldr Fork Leaf
-ofList (x:xs) = Fork x (ofList xs)
 
-toNumber :: T -> Either String Int
+toNumber :: T -> Either String Integer
 toNumber Leaf = Right 0
 toNumber (Fork Leaf rest) = case toNumber rest of
   Right n -> Right (2 * n)
@@ -102,7 +108,7 @@ toNumber _ = Left "Invalid Tree Calculus number"
 
 toString :: T -> Either String String
 toString tc = case toList tc of
-  Right list -> traverse (fmap toEnum . toNumber) list
+  Right list -> traverse (fmap (toEnum . fromInteger) . toNumber) list
   Left err -> Left "Invalid Tree Calculus string"
 
 toList :: T -> Either String [T]
@@ -113,20 +119,20 @@ toList (Fork x rest) = case toList rest of
 toList _ = Left "Invalid Tree Calculus list"
 
 -- Outputs
-formatResult :: EvaluatedForm -> T -> String
+formatT :: EvaluatedForm -> T -> String
-formatResult TreeCalculus = toSimpleT . show
+formatT TreeCalculus = toSimpleT . show
-formatResult FSL          = show
+formatT FSL          = show
-formatResult AST          = show . toAST
+formatT AST          = show . toAST
-formatResult Ternary      = toTernaryString
+formatT Ternary      = toTernaryString
-formatResult Ascii        = toAscii
+formatT Ascii        = toAscii
-formatResult Decode       = decodeResult
+formatT Decode       = decodeResult
 
 toSimpleT :: String -> String
 toSimpleT s = T.unpack
   $ replace "Fork" "t"
   $ replace "Stem" "t"
   $ replace "Leaf" "t"
-  $ (T.pack s)
+  $ T.pack s
 
 toTernaryString :: T -> String
 toTernaryString Leaf = "0"
@@ -153,8 +159,18 @@ toAscii tree = go tree "" True
         ++ go right (prefix ++ (if isLast then "    " else "|   ")) True
 
 decodeResult :: T -> String
-decodeResult tc
+decodeResult Leaf = "t"
-  | Right num  <- toNumber tc = show num
+decodeResult tc =
-  | Right str  <- toString tc = "\"" ++ str ++ "\""
+  case (toString tc, toList tc, toNumber tc) of
-  | Right list <- toList tc   = "[" ++ intercalate ", " (map decodeResult list) ++ "]"
+    (Right s, _, _) | all isCommonChar s -> "\"" ++ s ++ "\""
-  | otherwise                 = formatResult TreeCalculus tc
+    (_, _, Right n) -> show n
+    (_, Right xs@(_:_), _) -> "[" ++ intercalate ", " (map decodeResult xs) ++ "]"
+    (_, Right [], _) -> "[]"
+    _ -> formatT TreeCalculus tc
+  where
+    isCommonChar c =
+      let n = fromEnum c
+      in (n >= 32 && n <= 126)
+         || n == 9
+         || n == 10
+         || n == 13

test/Spec.hs

@@ -21,8 +21,8 @@ import qualified Data.Set as Set
 main :: IO ()
 main = defaultMain tests
 
-runTricu :: String -> String
+tricuTestString :: String -> String
-runTricu s = show $ result (evalTricu Map.empty $ parseTricu s)
+tricuTestString s = show $ result (evalTricu Map.empty $ parseTricu s)
 
 tests :: TestTree
 tests = testGroup "Tricu Tests"
@@ -30,10 +30,13 @@ tests = testGroup "Tricu Tests"
   , parser
   , simpleEvaluation
   , lambdas
-  , baseLibrary
+  , providedLibraries
   , fileEval
   , modules
   , demos
+  , decoding
+	, elimLambdaSingle
+	, stressElimLambda
   ]
 
 lexer :: TestTree
@@ -50,7 +53,22 @@ lexer = testGroup "Lexer Tests"
 
   , testCase "Lex escaped characters in strings" $ do
       let input = "\"hello\\nworld\""
-          expect = Right [LStringLiteral "hello\\nworld"]
+          expect = Right [LStringLiteral "hello\nworld"]
+      runParser tricuLexer "" input @?= expect
+
+  , testCase "Lex multiple escaped characters in strings" $ do
+      let input = "\"tab:\\t newline:\\n quote:\\\" backslash:\\\\\""
+          expect = Right [LStringLiteral "tab:\t newline:\n quote:\" backslash:\\"]
+      runParser tricuLexer "" input @?= expect
+
+  , testCase "Lex escaped characters in string literals" $ do
+      let input = "x = \"line1\\nline2\\tindented\""
+          expect = Right [LIdentifier "x", LAssign, LStringLiteral "line1\nline2\tindented"]
+      runParser tricuLexer "" input @?= expect
+
+  , testCase "Lex empty string with escape sequence" $ do
+      let input = "\"\\\"\""
+          expect = Right [LStringLiteral "\""]
       runParser tricuLexer "" input @?= expect
 
   , testCase "Lex mixed literals" $ do
@@ -86,7 +104,7 @@ parser = testGroup "Parser Tests"
         Right _ -> assertFailure "Expected failure when trying to assign the value of T"
 
   , testCase "Parse function definitions" $ do
-      let input = "x = (\\a b c : a)"
+      let input = "x = (a b c : a)"
           expect = SDef "x" [] (SLambda ["a"] (SLambda ["b"] (SLambda ["c"] (SVar "a"))))
       parseSingle input @?= expect
 
@@ -106,7 +124,7 @@ parser = testGroup "Parser Tests"
       parseSingle input @?= expect
 
   , testCase "Parse function with applications" $ do
-      let input  = "f = (\\x : t x)"
+      let input  = "f = (x : t x)"
           expect = SDef "f" [] (SLambda ["x"] (SApp TLeaf (SVar "x")))
       parseSingle input @?= expect
 
@@ -148,22 +166,22 @@ parser = testGroup "Parser Tests"
       parseSingle input @?= expect
 
   , testCase "Parse nested parentheses in function body" $ do
-      let input  = "f = (\\x : t (t (t t)))"
+      let input  = "f = (x : t (t (t t)))"
           expect = SDef "f" [] (SLambda ["x"] (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf))))
       parseSingle input @?= expect
 
   , testCase "Parse lambda abstractions" $ do
-      let input  = "(\\a : a)"
+      let input  = "(a : a)"
           expect = (SLambda ["a"] (SVar "a"))
       parseSingle input @?= expect
 
   , testCase "Parse multiple arguments to lambda abstractions" $ do
-      let input  = "x = (\\a b : a)"
+      let input  = "x = (a b : a)"
           expect = SDef "x" [] (SLambda ["a"] (SLambda ["b"] (SVar "a")))
       parseSingle input @?= expect
 
   , testCase "Grouping T terms with parentheses in function application" $ do
-      let input  = "x = (\\a : a)\nx (t)"
+      let input  = "x = (a : a)\nx (t)"
           expect = [SDef "x" [] (SLambda ["a"] (SVar "a")),SApp (SVar "x") TLeaf]
       parseTricu input @?= expect
 
@@ -250,7 +268,7 @@ simpleEvaluation = testGroup "Evaluation Tests"
   , testCase "Immutable definitions" $ do
       let input = "x = t t\nx = t\nx"
           env = evalTricu Map.empty (parseTricu input)
-      result <- try (evaluate (runTricu input)) :: IO (Either SomeException String)
+      result <- try (evaluate (tricuTestString input)) :: IO (Either SomeException String)
       case result of
         Left  _ -> return ()
         Right _ -> assertFailure "Expected evaluation error"
@@ -258,7 +276,7 @@ simpleEvaluation = testGroup "Evaluation Tests"
 
   , testCase "Apply identity to Boolean Not" $ do
       let not = "(t (t (t t) (t t t)) t)"
-      let input = "x = (\\a : a)\nx " ++ not
+      let input = "x = (a : a)\nx " ++ not
           env = evalTricu Map.empty (parseTricu input)
       result env @?= Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) Leaf
   ]
@@ -266,214 +284,182 @@ simpleEvaluation = testGroup "Evaluation Tests"
 lambdas :: TestTree
 lambdas = testGroup "Lambda Evaluation Tests"
   [ testCase "Lambda Identity Function" $ do
-      let input = "id = (\\x : x)\nid t"
+      let input = "id = (x : x)\nid t"
-      runTricu input @?= "Leaf"
+      tricuTestString input @?= "Leaf"
 
   , testCase "Lambda Constant Function (K combinator)" $ do
-      let input = "k = (\\x y : x)\nk t (t t)"
+      let input = "k = (x y : x)\nk t (t t)"
-      runTricu input @?= "Leaf"
+      tricuTestString input @?= "Leaf"
 
   , testCase "Lambda Application with Variable" $ do
-      let input = "id = (\\x : x)\nval = t t\nid val"
+      let input = "id = (x : x)\nval = t t\nid val"
-      runTricu input @?= "Stem Leaf"
+      tricuTestString input @?= "Stem Leaf"
 
   , testCase "Lambda Application with Multiple Arguments" $ do
-      let input = "apply = (\\f x y : f x y)\nk = (\\a b : a)\napply k t (t t)"
+      let input = "apply = (f x y : f x y)\nk = (a b : a)\napply k t (t t)"
-      runTricu input @?= "Leaf"
+      tricuTestString input @?= "Leaf"
 
    , testCase "Nested Lambda Application" $ do
-      let input = "apply = (\\f x y : f x y)\nid = (\\x : x)\napply (\\f x : f x) id t"
+      let input = "apply = (f x y : f x y)\nid = (x : x)\napply (f x : f x) id t"
-      runTricu input @?= "Leaf"
+      tricuTestString input @?= "Leaf"
 
   , testCase "Lambda with a complex body" $ do
-      let input = "f = (\\x : t (t x))\nf t"
+      let input = "f = (x : t (t x))\nf t"
-      runTricu input @?= "Stem (Stem Leaf)"
+      tricuTestString input @?= "Stem (Stem Leaf)"
 
   , testCase "Lambda returning a function" $ do
-      let input = "f = (\\x : (\\y : x))\ng = f t\ng (t t)"
+      let input = "f = (x : (y : x))\ng = f t\ng (t t)"
-      runTricu input @?= "Leaf"
+      tricuTestString input @?= "Leaf"
 
   , testCase "Lambda with Shadowing" $ do
-      let input = "f = (\\x : (\\x : x))\nf t (t t)"
+      let input = "f = (x : (x : x))\nf t (t t)"
-      runTricu input @?= "Stem Leaf"
+      tricuTestString input @?= "Stem Leaf"
 
    , testCase "Lambda returning another lambda" $ do
-      let input = "k = (\\x : (\\y : x))\nk_app = k t\nk_app (t t)"
+      let input = "k = (x : (y : x))\nk_app = k t\nk_app (t t)"
-      runTricu input @?= "Leaf"
+      tricuTestString input @?= "Leaf"
 
    , testCase "Lambda with free variables" $ do
-      let input = "y = t t\nf = (\\x : y)\nf t"
+      let input = "y = t t\nf = (x : y)\nf t"
-      runTricu input @?= "Stem Leaf"
+      tricuTestString input @?= "Stem Leaf"
 
    , testCase "SKI Composition" $ do
-      let input = "s = (\\x y z : x z (y z))\nk = (\\x y : x)\ni = (\\x : x)\ncomp = s k i\ncomp t (t t)"
+      let input = "s = (x y z : x z (y z))\nk = (x y : x)\ni = (x : x)\ncomp = s k i\ncomp t (t t)"
-      runTricu input @?= "Stem (Stem Leaf)"
+      tricuTestString input @?= "Stem (Stem Leaf)"
 
    , testCase "Lambda with multiple parameters and application" $ do
-      let input = "f = (\\a b c : t a b c)\nf t (t t) (t t t)"
+      let input = "f = (a b c : t a b c)\nf t (t t) (t t t)"
-      runTricu input @?= "Stem Leaf"
+      tricuTestString input @?= "Stem Leaf"
 
    , testCase "Lambda with nested application in the body" $ do
-      let input = "f = (\\x : t (t (t x)))\nf t"
+      let input = "f = (x : t (t (t x)))\nf t"
-      runTricu input @?= "Stem (Stem (Stem Leaf))"
+      tricuTestString input @?= "Stem (Stem (Stem Leaf))"
 
     , testCase "Lambda returning a function and applying it" $ do
-        let input = "f = (\\x : (\\y : t x y))\ng = f t\ng (t t)"
+        let input = "f = (x : (y : t x y))\ng = f t\ng (t t)"
-        runTricu input @?= "Fork Leaf (Stem Leaf)"
+        tricuTestString input @?= "Fork Leaf (Stem Leaf)"
 
     , testCase "Lambda applying a variable" $ do
-        let input = "id = (\\x : x)\na = t t\nid a"
+        let input = "id = (x : x)\na = t t\nid a"
-        runTricu input @?= "Stem Leaf"
+        tricuTestString input @?= "Stem Leaf"
 
     , testCase "Nested lambda abstractions in the same expression" $ do
-        let input = "f = (\\x : (\\y : x y))\ng = (\\z : z)\nf g t"
+        let input = "f = (x : (y : x y))\ng = (z : z)\nf g t"
-        runTricu input @?= "Leaf"
+        tricuTestString input @?= "Leaf"
 
-  , testCase "Lambda with a string literal" $ do
+  , testCase "Lambda applied to string literal" $ do
-        let input = "f = (\\x : x)\nf \"hello\""
+        let input = "f = (x : x)\nf \"hello\""
-        runTricu input @?= "Fork (Fork Leaf (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) Leaf))))"
+        tricuTestString input @?= "Fork (Fork Leaf (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork Leaf (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) (Fork (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork (Stem Leaf) Leaf))))))) Leaf))))"
 
 
-   , testCase "Lambda with an integer literal" $ do
+   , testCase "Lambda applied to integer literal" $ do
-        let input = "f = (\\x : x)\nf 42"
+        let input = "f = (x : x)\nf 42"
-        runTricu input @?= "Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) Leaf)))))"
+        tricuTestString input @?= "Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) (Fork Leaf (Fork (Stem Leaf) Leaf)))))"
 
-   , testCase "Lambda with a list literal" $ do
+   , testCase "Lambda applied to list literal" $ do
-        let input = "f = (\\x : x)\nf [t (t t)]"
+        let input = "f = (x : x)\nf [t (t t)]"
-        runTricu input @?= "Fork Leaf (Fork (Stem Leaf) Leaf)"
+        tricuTestString input @?= "Fork Leaf (Fork (Stem Leaf) Leaf)"
+
+  , testCase "Lambda containing list literal" $ do
+      let input = "(a : [(a)]) 1"
+      tricuTestString input @?= "Fork (Fork (Stem Leaf) Leaf) Leaf"
   ]
 
-baseLibrary :: TestTree
+providedLibraries :: TestTree
-baseLibrary = testGroup "Library Tests"
+providedLibraries = testGroup "Library Tests"
-  [ testCase "K combinator 1" $ do
+  [ testCase "Triage test Leaf" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
-      let input = "k (t) (t t)"
-          env = evalTricu library (parseTricu input)
-      result env @?= Leaf
-
-  , testCase "K combinator 2" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "k (t t) (t)"
-          env = evalTricu library (parseTricu input)
-      result env @?= Stem Leaf
-
-  , testCase "K combinator 3" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "k (t t t) (t)"
-          env = evalTricu library (parseTricu input)
-      result env @?= Fork Leaf Leaf
-
-  , testCase "S combinator" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "s (t) (t) (t)"
-          env = evalTricu library (parseTricu input)
-      result env @?= Fork Leaf (Stem Leaf)
-
-  , testCase "SKK == I (fully expanded)" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "s k k"
-          env = evalTricu library (parseTricu input)
-      result env @?= Fork (Stem (Stem Leaf)) (Stem Leaf)
-
-  , testCase "I combinator" $ do
-      library <- evaluateFile "./lib/base.tri"
-      let input = "i not?"
-          env = evalTricu library (parseTricu input)
-      result env @?= Fork (Fork (Stem Leaf) (Fork Leaf Leaf)) (Fork Leaf (Fork Leaf Leaf))
-
-  , testCase "Triage test Leaf" $ do
-      library <- evaluateFile "./lib/base.tri"
       let input = "test t"
           env = decodeResult $ result $ evalTricu library (parseTricu input)
       env @?= "\"Leaf\""
 
   , testCase "Triage test (Stem Leaf)" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "test (t t)"
           env = decodeResult $ result $ evalTricu library (parseTricu input)
       env @?= "\"Stem\""
 
   , testCase "Triage test (Fork Leaf Leaf)" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "test (t t t)"
           env = decodeResult $ result $ evalTricu library (parseTricu input)
       env @?= "\"Fork\""
 
   , testCase "Boolean NOT: true" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "not? true"
           env = result $ evalTricu library (parseTricu input)
       env @?= Leaf
 
   , testCase "Boolean NOT: false" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "not? false"
           env = result $ evalTricu library (parseTricu input)
       env @?= Stem Leaf
 
 
   , testCase "Boolean AND TF" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "and? (t t) (t)"
           env = evalTricu library (parseTricu input)
       result env @?= Leaf
 
   , testCase "Boolean AND FT" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "and? (t) (t t)"
           env = evalTricu library (parseTricu input)
       result env @?= Leaf
 
   , testCase "Boolean AND FF" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "and? (t) (t)"
           env = evalTricu library (parseTricu input)
       result env @?= Leaf
 
   , testCase "Boolean AND TT" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "and? (t t) (t t)"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
 
   , testCase "List head" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "head [(t) (t t) (t t t)]"
           env = evalTricu library (parseTricu input)
       result env @?= Leaf
 
   , testCase "List tail" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "head (tail (tail [(t) (t t) (t t t)]))"
           env = evalTricu library (parseTricu input)
       result env @?= Fork Leaf Leaf
 
   , testCase "List map" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
-      let input = "head (tail (map (\\a : (t t t)) [(t) (t) (t)]))"
+      let input = "head (tail (map (a : (t t t)) [(t) (t) (t)]))"
           env = evalTricu library (parseTricu input)
       result env @?= Fork Leaf Leaf
 
   , testCase "Empty list check" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "emptyList? []"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
 
   , testCase "Non-empty list check" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "not? (emptyList? [(1) (2) (3)])"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
 
   , testCase "Concatenate strings" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "append \"Hello, \" \"world!\""
           env = decodeResult $ result $ evalTricu library (parseTricu input)
       env @?= "\"Hello, world!\""
 
   , testCase "Verifying Equality" $ do
-      library <- evaluateFile "./lib/base.tri"
+      library <- evaluateFile "./lib/list.tri"
       let input = "equal? (t t t) (t t t)"
           env = evalTricu library (parseTricu input)
       result env @?= Stem Leaf
@@ -490,12 +476,12 @@ fileEval = testGroup "File evaluation tests"
       res @?= Fork (Stem Leaf) Leaf
 
   , testCase "Mapping and Equality" $ do
-      library <- liftIO $ evaluateFile "./lib/base.tri"
+      library <- liftIO $ evaluateFile "./lib/list.tri"
       fEnv    <- liftIO $ evaluateFileWithContext library "./test/map.tri"
       (mainResult fEnv) @?= Stem Leaf
 
   , testCase "Eval and decoding string" $ do
-      library <- liftIO $ evaluateFile "./lib/base.tri"
+      library <- liftIO $ evaluateFile "./lib/list.tri"
       res <- liftIO $ evaluateFileWithContext library "./test/string.tri"
       decodeResult (result res) @?= "\"String test!\""
   ]
@@ -549,8 +535,109 @@ demos = testGroup "Test provided demo functionality"
       decodeResult res @?= "\"(t (t (t t) (t t t)) (t t (t t t)))\""
   , testCase "Determining the size of functions" $ do
       res     <- liftIO $ evaluateFileResult "./demos/size.tri"
-      decodeResult res @?= "454"
+      decodeResult res @?= "321"
   , testCase "Level Order Traversal demo" $ do
       res     <- liftIO $ evaluateFileResult "./demos/levelOrderTraversal.tri"
       decodeResult res @?= "\"\n1 \n2 3 \n4 5 6 7 \n8 11 10 9 12 \""
   ]
+
+decoding :: TestTree
+decoding = testGroup "Decoding Tests"
+  [ testCase "Decode Leaf" $ do
+      decodeResult Leaf @?= "t"
+
+  , testCase "Decode list of non-ASCII numbers" $ do
+      let input = ofList [ofNumber 1, ofNumber 14, ofNumber 6]
+      decodeResult input @?= "[1, 14, 6]"
+
+  , testCase "Decode list of ASCII numbers as a string" $ do
+      let input = ofList [ofNumber 97, ofNumber 98, ofNumber 99]
+      decodeResult input @?= "\"abc\""
+
+  , testCase "Decode small number" $ do
+      decodeResult (ofNumber 42) @?= "42"
+
+  , testCase "Decode large number" $ do
+      decodeResult (ofNumber 9999) @?= "9999"
+
+  , testCase "Decode string in list" $ do
+      let input = ofList [ofString "hello", ofString "world"]
+      decodeResult input @?= "[\"hello\", \"world\"]"
+
+  , testCase "Decode mixed list with strings" $ do
+      let input = ofList [ofString "hello", ofNumber 42, ofString "world"]
+      decodeResult input @?= "[\"hello\", 42, \"world\"]"
+
+  , testCase "Decode nested lists with strings" $ do
+      let input = ofList [ofList [ofString "nested"], ofString "string"]
+      decodeResult input @?= "[[\"nested\"], \"string\"]"
+  ]
+
+elimLambdaSingle :: TestTree
+elimLambdaSingle = testCase "elimLambda preserves eval, fires eta, and SDef binds" $ do
+  -- 1) eta reduction, purely structural and parsed from source
+  let [etaIn] = parseTricu "x : f x"
+      [fRef ] = parseTricu "f"
+  elimLambda etaIn @?= fRef
+
+  -- 2) SDef binds its own name and parameters
+  let [defFXY] = parseTricu "f x y : f x"
+      fv       = freeVars defFXY
+  assertBool "f should be bound in SDef" ("f" `Set.notMember` fv)
+  assertBool "x should be bound in SDef" ("x" `Set.notMember` fv)
+  assertBool "y should be bound in SDef" ("y" `Set.notMember` fv)
+
+  -- 3) semantics preserved on a small program that exercises compose and triage
+  let src =
+        unlines
+          [ "false = t"
+          , "_     = t"
+          , "true  = t t"
+          , "id    = a : a"
+          , "const = a b : a"
+          , "compose = f g x : f (g x)"
+          , "triage = leaf stem fork : t (t leaf stem) fork"
+          , "test   = triage \"Leaf\" (_ : \"Stem\") (_ _ : \"Fork\")"
+          , "main   = compose id id test"
+          ]
+      prog        = parseTricu src
+      progElim    = map elimLambda prog
+      evalBefore  = result (evalTricu Map.empty prog)
+      evalAfter   = result (evalTricu Map.empty progElim)
+  evalAfter @?= evalBefore
+
+stressElimLambda :: TestTree
+stressElimLambda = testCase "stress elimLambda on wide list under deep curried lambda" $ do
+  let numVars = 200
+      numBody = 800
+      vars    = [ "x" ++ show i | i <- [1..numVars] ]
+      body    = "(" ++ unwords (replicate numBody "t") ++ ")"
+      etaOne  = "h : f h"
+      etaTwo  = "k : id k"
+      defId   = "id = a : a"
+      lambda  = unwords vars ++ " : " ++ body
+      src     = unlines
+                  [ defId
+                  , etaOne
+                  , "compose = f g x : f (g x)"
+                  , "f = t t"
+                  , etaTwo
+                  , lambda
+                  , "main = compose id id (" ++ head vars ++ " : f " ++ head vars ++ ")"
+                  ]
+      prog    = parseTricu src
+
+  let out = map elimLambda prog
+  let noLambda term = case term of
+        SLambda _ _ -> False
+        SApp f g    -> noLambda f && noLambda g
+        SList xs    -> all noLambda xs
+        TFork l r   -> noLambda l && noLambda r
+        TStem u     -> noLambda u
+        _           -> True
+
+  assertBool "all lambdas eliminated" (all noLambda out)
+
+  let before = result (evalTricu Map.empty prog)
+      after  = result (evalTricu Map.empty out)
+  after @?= before

test/comments-1.tri

@@ -1,9 +1,9 @@
 -- This is a tricu comment!
 -- t (t t) (t (t t t))
 -- t (t t t) (t t)
--- x = (\a : a)
+-- x = (a : a)
 main = t (t t) t -- Fork (Stem Leaf) Leaf
 -- t t
 -- x
--- x = (\a : a)
+-- x = (a : a)
 -- t

test/cycle-1.tri

@@ -1,4 +1,4 @@
 
-!import "test/cycle-2.tri" Cycle2
+!import "cycle-2.tri" Cycle2
 
 cycle1 = t Cycle2.cycle2

test/cycle-2.tri

@@ -1,4 +1,4 @@
 
-!import "test/cycle-1.tri" Cycle1
+!import "cycle-1.tri" Cycle1
 
 cycle2 = t Cycle1.cycle1

test/lambda-A.tri

@@ -1 +1 @@
-main = (\x : x) t
+main = (x : x) t

test/local-ns/1.tri

@@ -1,4 +1,4 @@
 
-!import "test/local-ns/2.tri" Two
+!import "2.tri" Two
 
 main = Two.x

test/local-ns/2.tri

@@ -1,2 +1,2 @@
 
-!import "test/local-ns/3.tri" !Local
+!import "3.tri" !Local

test/local-ns/3.tri

@@ -1,2 +1 @@
-
 x = 3

test/map.tri

@@ -1,2 +1,2 @@
-x = map (\i : append "Successfully concatenated " i) [("two strings!")]
+x = map (i : append "Successfully concatenated " i) [("two strings!")]
 main = equal? x [("Successfully concatenated two strings!")]

test/multi-level-A.tri

@@ -1,2 +1,2 @@
-!import "./test/multi-level-B.tri" B
+!import "multi-level-B.tri" B
 main = B.main

test/multi-level-B.tri

@@ -1,2 +1,2 @@
-!import "./test/multi-level-C.tri" C
+!import "multi-level-C.tri" C
 main = C.val

test/namespace-A.tri

@@ -1,2 +1,2 @@
-!import "./test/namespace-B.tri" B
+!import "namespace-B.tri" B
 main = B.x

test/size.tri

@@ -1,21 +1,21 @@
-compose = \f g x : f (g x)
+compose = f g x : f (g x)
 
-succ = y (\self :
+succ = y (self :
   triage
     1
     t
     (triage
       (t (t t))
-      (\_ tail : t t (self tail))
+      (_ tail : t t (self tail))
       t))
 
-size = (\x :
+size = (x :
-  (y (\self x :
+  (y (self x :
     compose succ
       (triage
-        (\x : x)
+        (x : x)
         self
-        (\x y : compose (self x) (self y))
+        (x y : compose (self x) (self y))
         x)) x 0))
 
 size size

test/string.tri

@@ -1 +1 @@
-head (map (\i : append "String " i) [("test!")])
+head (map (i : append "String " i) [("test!")])

test/vars-A.tri

@@ -1,6 +1,6 @@
 
-!import "./test/vars-B.tri" B
+!import "vars-B.tri" B
 
-!import "./test/vars-C.tri" C
+!import "vars-C.tri" C
 
 main = B.y (C.z)

test/vars-B.tri

@@ -1 +1 @@
-y = \x : x
+y = x : x

tricu.cabal

@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           tricu
-version:        0.13.0
+version:        0.19.0
 description:    A micro-language for exploring Tree Calculus
 author:         James Eversole
 maintainer:     james@eversole.co
@@ -27,10 +27,12 @@ executable tricu
     , cmdargs
     , containers
     , exceptions
+    , filepath
     , haskeline
     , megaparsec
     , mtl
     , text
+    , transformers
   other-modules:
     Eval
     FileEval
@@ -54,6 +56,7 @@ test-suite tricu-tests
     , cmdargs
     , containers
     , exceptions
+    , filepath
     , haskeline
     , megaparsec
     , mtl
@@ -61,6 +64,7 @@ test-suite tricu-tests
     , tasty-hunit
     , tasty-quickcheck
     , text
+    , transformers
   default-language:    Haskell2010
   other-modules:
     Eval