pow, even, odd, min, max

AGENTS.md

@@ -16,6 +16,26 @@ nix build .#
 
 > **Rule of thumb:** if it builds, links, or tests, it goes through `nix`.
 
+### Write and test, don't mentally trace
+
+`nix flake check` finishes quickly. Use it.
+
+tricu's minimalism makes it easy to build a confident-sounding but wrong
+mental model of evaluation order, branch selection (`matchBool` arg order),
+or number encoding. A quick test replaces many minutes of uncertain reasoning.
+
+Prefer:
+
+1. Write a candidate implementation.
+2. Run the tests or a probe.
+3. Fix what's wrong.
+
+Over:
+
+1. Reason about semantics across multiple files.
+2. Build up a chain of inference.
+3. Write code that assumes the chain was correct.
+
 ## Project Overview
 
 **tricu** (pronounced "tree-shoe") is a programming-language experiment written primarily in Haskell.

lib/base.tri

@@ -246,6 +246,24 @@ mod = y (self a b :
       (_ : a)
       (_ : self (sub a b) b)))
 
+pow = y (self a b :
+  ifLazy
+    (isZero? b)
+    (_ : 1)
+    (_ : mul a (self a (pred b))))
+
+even? n = (triage
+  true
+  (_ : false)
+  (bit _ : isZero? bit)
+  n)
+
+odd? = (n : not? (even? n))
+
+min = (a b : ifLazy (lte? a b) (_ : a) (_ : b))
+
+max = (a b : ifLazy (lte? a b) (_ : b) (_ : a))
+
 -- ---------------------------------------------------------------------------
 -- Result combinators
 -- ---------------------------------------------------------------------------

test/Spec.hs

@@ -1435,6 +1435,121 @@ arithmetic = testGroup "Arithmetic Tests"
       let input = "equal? (add (mul 3 7) 4) 25"
           env = evalTricu allTestLibsEnv (parseTricu input)
       result env @?= trueT
+
+  , testCase "pow 2 0 = 1" $ do
+      let input = "pow 2 0"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 1
+
+  , testCase "pow 2 3 = 8" $ do
+      let input = "pow 2 3"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 8
+
+  , testCase "pow 3 2 = 9" $ do
+      let input = "pow 3 2"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 9
+
+  , testCase "pow 0 0 = 1" $ do
+      let input = "pow 0 0"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 1
+
+  , testCase "pow 0 5 = 0" $ do
+      let input = "pow 0 5"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 0
+
+  , testCase "pow 1 10 = 1" $ do
+      let input = "pow 1 10"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 1
+
+  , testCase "pow 5 1 = 5" $ do
+      let input = "pow 5 1"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 5
+
+  , testCase "min 3 7 = 3" $ do
+      let input = "min 3 7"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 3
+
+  , testCase "min 7 3 = 3" $ do
+      let input = "min 7 3"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 3
+
+  , testCase "min 5 5 = 5" $ do
+      let input = "min 5 5"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 5
+
+  , testCase "min 0 5 = 0" $ do
+      let input = "min 0 5"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 0
+
+  , testCase "max 3 7 = 7" $ do
+      let input = "max 3 7"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 7
+
+  , testCase "max 7 3 = 7" $ do
+      let input = "max 7 3"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 7
+
+  , testCase "max 5 5 = 5" $ do
+      let input = "max 5 5"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 5
+
+  , testCase "max 0 5 = 5" $ do
+      let input = "max 0 5"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 5
+
+  , testCase "even? 0 = true" $ do
+      let input = "even? 0"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= trueT
+
+  , testCase "even? 1 = false" $ do
+      let input = "even? 1"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= falseT
+
+  , testCase "even? 2 = true" $ do
+      let input = "even? 2"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= trueT
+
+  , testCase "even? 7 = false" $ do
+      let input = "even? 7"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= falseT
+
+  , testCase "odd? 0 = false" $ do
+      let input = "odd? 0"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= falseT
+
+  , testCase "odd? 1 = true" $ do
+      let input = "odd? 1"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= trueT
+
+  , testCase "odd? 2 = false" $ do
+      let input = "odd? 2"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= falseT
+
+  , testCase "odd? 7 = true" $ do
+      let input = "odd? 7"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= trueT
   ]
 
 fileEval :: TestTree