From dfcaf14404085898345781f09b0ee4576c7f9059 Mon Sep 17 00:00:00 2001
From: James Eversole <james@eversole.co>
Date: Sun, 30 Aug 2026 09:56:22 -0500
Subject: [PATCH] Division and fixed pred

---
 lib/base.tri | 35 ++++++++++++++++++++--------
 test/Spec.hs | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 88 insertions(+), 12 deletions(-)

diff --git a/lib/base.tri b/lib/base.tri
index 7955361..620f7a4 100644
--- a/lib/base.tri
+++ b/lib/base.tri
@@ -178,18 +178,15 @@ andLazy? = (a bK :
 
 pred = y (self : triage
   0
-  (_ : 0)
+  0
   (bit rest :
-    matchBool
-      (matchBool
+    ifLazy
+      bit
+      (_ : matchBool
+        (t t rest)
         0
-        (pair 0 rest)
-        (equal? rest 0))
-      (matchBool
-        0
-        (pair 1 (self rest))
-        (equal? rest 0))
-      bit))
+        rest)
+      (_ : t (t t) (self rest))))
 
 isZero? = triage true (_ : false) (_ _ : false)
 
@@ -231,6 +228,24 @@ mul = y (self a b :
     (_ : 0)
     (_ : add a (self a (pred b))))
 
+div = y (self a b :
+  ifLazy
+    (isZero? b)
+    (_ : 0)
+    (_ : ifLazy
+      (lt? a b)
+      (_ : 0)
+      (_ : succ (self (sub a b) b))))
+
+mod = y (self a b :
+  ifLazy
+    (isZero? b)
+    (_ : 0)
+    (_ : ifLazy
+      (lt? a b)
+      (_ : a)
+      (_ : self (sub a b) b)))
+
 -- ---------------------------------------------------------------------------
 -- Result combinators
 -- ---------------------------------------------------------------------------
diff --git a/test/Spec.hs b/test/Spec.hs
index 5a50522..db8d068 100644
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -80,6 +80,7 @@ tests = testGroup "Tricu Tests"
   --, parser
   --, simpleEvaluation
   --, lambdas
+  , arithmetic
   , providedLibraries
   --, maybeTests
   --, fileEval
@@ -1193,8 +1194,8 @@ providedLibraries = testGroup "Library Tests"
       result env @?= ofString ""
   ]
 
-arithmeticTests :: TestTree
-arithmeticTests = testGroup "Arithmetic Tests"
+arithmetic :: TestTree
+arithmetic = testGroup "Arithmetic Tests"
   [ testCase "isZero? on 0" $ do
       let input = "isZero? 0"
           env = evalTricu allTestLibsEnv (parseTricu input)
@@ -1374,6 +1375,66 @@ arithmeticTests = testGroup "Arithmetic Tests"
       let input = "isZero? (add 0 0)"
           env = evalTricu allTestLibsEnv (parseTricu input)
       result env @?= trueT
+
+  , testCase "div 10 3 = 3" $ do
+      let input = "div 10 3"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 3
+
+  , testCase "div 12 4 = 3 (exact)" $ do
+      let input = "div 12 4"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 3
+
+  , testCase "div 3 5 = 0 (divisor larger)" $ do
+      let input = "div 3 5"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 0
+
+  , testCase "div 7 1 = 7 (identity)" $ do
+      let input = "div 7 1"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 7
+
+  , testCase "div 0 5 = 0" $ do
+      let input = "div 0 5"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 0
+
+  , testCase "div 5 0 = 0 (div by zero)" $ do
+      let input = "div 5 0"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 0
+
+  , testCase "mod 10 3 = 1" $ do
+      let input = "mod 10 3"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 1
+
+  , testCase "mod 12 4 = 0 (exact)" $ do
+      let input = "mod 12 4"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 0
+
+  , testCase "mod 3 5 = 3 (divisor larger)" $ do
+      let input = "mod 3 5"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 3
+
+  , testCase "mod 7 1 = 0" $ do
+      let input = "mod 7 1"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 0
+
+  , testCase "mod 5 0 = 0 (mod by zero)" $ do
+      let input = "mod 5 0"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= ofNumber 0
+
+  , testCase "div mod consistency" $ do
+      let input = "equal? (add (mul 3 7) 4) 25"
+          env = evalTricu allTestLibsEnv (parseTricu input)
+      result env @?= trueT
   ]
 
 fileEval :: TestTree