Automatic decoding of supported literals in REPL

Automatic decoding & display of string, number, and list types in REPL.
General updates to README, style, and comments.

src/Eval.hs

@@ -11,8 +11,7 @@ import qualified Data.Set as Set
 evalSingle :: Map String T -> SaplingAST -> Map String T
 evalSingle env term = case term of
   SFunc name [] body ->
-    let
-        lineNoLambda = eliminateLambda body
+    let lineNoLambda = eliminateLambda body
         result = evalAST env lineNoLambda
     in Map.insert name result env
   SLambda _ body ->
@@ -67,6 +66,9 @@ eliminateLambda (TFork l r) = TFork (eliminateLambda l) (eliminateLambda r)
 eliminateLambda (SList xs) = SList (map eliminateLambda xs)
 eliminateLambda other = other
 
+-- This is my attempt to implement the lambda calculus elimination rules defined
+-- in "Typed Program Analysis without Encodings" by Barry Jay.
+-- https://github.com/barry-jay-personal/typed_tree_calculus/blob/main/typed_program_analysis.pdf
 lambdaToT :: String -> SaplingAST -> SaplingAST
 lambdaToT x (SVar y)
   | x == y = tI
@@ -101,6 +103,8 @@ toAST Leaf = TLeaf
 toAST (Stem a) = TStem (toAST a)
 toAST (Fork a b) = TFork (toAST a) (toAST b)
 
+-- We need the SKI operators in an unevaluated SaplingAST tree form so that we
+-- can keep the evaluation functions straightforward
 tI :: SaplingAST
 tI = SApp (SApp TLeaf (SApp TLeaf (SApp TLeaf TLeaf))) TLeaf