boot2

commit b00065b8511ec5507c85584bdeddc5a02e1bb059
parent 602a59d9deda0b87d23dac8403305bc861227249
Author: Ryan Sepassi <rsepassi@gmail.com>
Date:   Sat, 25 Apr 2026 14:33:10 -0700

scheme1: add min, max, modulo to the prelude

min/max are 2-arg derivations from <. modulo is the floor-flavor
companion to the truncating remainder primitive: same value when r
and b share a sign, +b adjustment otherwise. Tests in 71-quot-rem-mod
and 72-min-max-abs (previously red) cover all sign combinations.

Diffstat:
M
scheme1/prelude.scm
 | 
14
++++++++++++++

1 file changed, 14 insertions(+), 0 deletions(-)
diff --git a/scheme1/prelude.scm b/scheme1/prelude.scm
@@ -16,6 +16,20 @@
 
 (define (abs x) (if (< x 0) (- 0 x) x))
 
+(define (min a b) (if (< a b) a b))
+(define (max a b) (if (< a b) b a))
+
+;; modulo has the sign of the divisor; remainder has the sign of the
+;; dividend. They differ exactly when r is nonzero and r and b have
+;; opposite signs -- in that case adjust by adding b.
+(define (modulo a b)
+  (let ((r (remainder a b)))
+    (if (zero? r)
+        0
+        (if (eq? (negative? r) (negative? b))
+            r
+            (+ r b)))))
+
 ;; --- Common c*r compositions ---------------------------------------
 (define (caar x)  (car (car x)))
 (define (cadr x)  (car (cdr x)))