From 819179c5838e9a2ebba69d5569f3c08d093194d2 Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Sat, 17 Jan 2026 13:52:49 -0500
Subject: Simplify equality checks for common cases.

---
 src/stdlib/reals.c | 35 ++++++++++++++++++++++++++++++++++-
 src/stdlib/reals.h |  1 +
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/stdlib/reals.c b/src/stdlib/reals.c
index bbe19d0d..c7b101b6 100644
--- a/src/stdlib/reals.c
+++ b/src/stdlib/reals.c
@@ -211,6 +211,7 @@ public
 Real_t Real$minus(Real_t a, Real_t b) {
     if (Real$is_zero(b)) return a;
     else if (Real$is_zero(a)) return Real$negative(b);
+    else if (Real$obviously_equal(a, b)) return R(0);
 
     if (!Real$is_boxed(a) && !Real$is_boxed(b)) {
         feclearexcept(FE_INEXACT);
@@ -270,6 +271,10 @@ Real_t Real$times(Real_t a, Real_t b) {
         }
     }
 
+    // Prefer putting symbolic in RHS to make simplifying easier
+    if (Real$tag(a) == REAL_TAG_SYMBOLIC && Real$tag(b) != REAL_TAG_SYMBOLIC)
+        return sym_to_real(.op = SYM_MUL, .left = b, .right = a);
+
     return sym_to_real(.op = SYM_MUL, .left = a, .right = b);
 }
 
@@ -738,9 +743,35 @@ PUREFUNC bool Real$is_none(const void *vn, const TypeInfo_t *type) {
 
 // Equality check (may be undecidable for some symbolics)
 public
-bool Real$equal_values(Real_t a, Real_t b) {
+PUREFUNC bool Real$obviously_equal(Real_t a, Real_t b) {
     if (a.bits == b.bits) return true;
     if (!Real$is_boxed(a) && !Real$is_boxed(b)) return REAL_DOUBLE(a) == REAL_DOUBLE(b);
+    if (Real$tag(a) != Real$tag(b)) return false;
+
+    switch (Real$tag(a)) {
+    case REAL_TAG_BIGINT: {
+        return Int$equal_value(*REAL_BIGINT(a), *REAL_BIGINT(b));
+    }
+    case REAL_TAG_RATIONAL: {
+        rational_t *ra = REAL_RATIONAL(a);
+        rational_t *rb = REAL_RATIONAL(b);
+        return mpq_equal(&ra->value, &rb->value);
+    }
+    case REAL_TAG_SYMBOLIC: {
+        symbolic_t *sa = REAL_SYMBOLIC(a);
+        symbolic_t *sb = REAL_SYMBOLIC(b);
+        if (sa->op != sb->op) return false;
+        return Real$obviously_equal(sa->left, sb->left) && Real$obviously_equal(sa->right, sb->right);
+    }
+    default: return false;
+    }
+}
+
+// Equality check (may be undecidable for some symbolics)
+public
+bool Real$equal_values(Real_t a, Real_t b) {
+    if (Real$obviously_equal(a, b)) return true;
+    if (!Real$is_boxed(a) && !Real$is_boxed(b)) return REAL_DOUBLE(a) == REAL_DOUBLE(b);
 
     if (!Real$is_boxed(a)) a = Real$as_rational(REAL_DOUBLE(a));
     if (!Real$is_boxed(b)) b = Real$as_rational(REAL_DOUBLE(b));
@@ -779,6 +810,8 @@ int32_t Real$compare_values(Real_t a, Real_t b) {
         return (REAL_DOUBLE(a) > REAL_DOUBLE(b)) - (REAL_DOUBLE(a) < REAL_DOUBLE(b));
     }
 
+    if (Real$obviously_equal(a, b)) return 0;
+
     if (Real$tag(a) == REAL_TAG_RATIONAL && Real$tag(b) == REAL_TAG_RATIONAL) {
         rational_t *ra = REAL_RATIONAL(a);
         rational_t *rb = REAL_RATIONAL(b);
diff --git a/src/stdlib/reals.h b/src/stdlib/reals.h
index 13f9cea3..ae1ba968 100644
--- a/src/stdlib/reals.h
+++ b/src/stdlib/reals.h
@@ -48,6 +48,7 @@ Text_t Real$as_text(const void *n, bool colorize, const TypeInfo_t *type);
 Text_t Real$value_as_text(Real_t x);
 bool Real$equal(const void *va, const void *vb, const TypeInfo_t *t);
 bool Real$equal_values(Real_t a, Real_t b);
+PUREFUNC bool Real$obviously_equal(Real_t a, Real_t b);
 bool Real$get_rational(Real_t x, int64_t *num, int64_t *den);
 bool Real$is_between(Real_t x, Real_t low, Real_t high);
 double Real$as_float64(Real_t n, bool truncate);
-- 
cgit v1.2.3