tisp

commit c2747457ab8d62e36ae74cd178b75e6fba1c3e45
parent 67a6ce0eee0870842777aa99cd5bca082830a2ed
Author: Ed van Bruggen <edvb@uw.edu>
Date:   Sun, 24 Nov 2019 23:56:51 -0800

Preserve number type with sgn

Diffstat:
test.c
 | 
18
+++++++++---------
tibs/lib.tsp
 | 
2
+-

2 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/test.c b/test.c
@@ -457,15 +457,15 @@ char *tests[][2] = {
 	{ "(abs -3/5)", "3/5" },
 	{ "(abs 0.0)",  "0.0" },
 
-	{ "sgn",         NULL },
-	{ "(sgn 239)",   "1"  },
-	{ "(sgn -3)",    "-1" },
-	{ "(sgn 5/4)",   "1"  },
-	{ "(sgn -1/7)",  "-1" },
-	{ "(sgn 3.17)",  "1"  },
-	{ "(sgn -.457)", "-1" },
-	{ "(sgn 0)",     "0"  },
-	{ "(sgn 0.0)",   "0"  },
+	{ "sgn",         NULL   },
+	{ "(sgn 239)",   "1"    },
+	{ "(sgn -3)",    "-1"   },
+	{ "(sgn 5/4)",   "1"    },
+	{ "(sgn -1/7)",  "-1"   },
+	{ "(sgn 3.17)",  "1.0"  },
+	{ "(sgn -.457)", "-1.0" },
+	{ "(sgn 0)",     "0"    },
+	{ "(sgn 0.0)",   "0"    },
 
 	{ "max/min",          NULL    },
 	{ "(max 9346 13297)", "13297" },
diff --git a/tibs/lib.tsp b/tibs/lib.tsp
@@ -221,7 +221,7 @@
 (define (arccot x) (/ (arctan x)))
 
 (define (abs x) (if (>= x 0) x (- x)))
-(define (sgn x) (cond ((= x 0) 0) ((> x 0) 1) (else -1)))
+(define (sgn x) (if (= x 0) 0 (/ (abs x) x)))
 (define (max a b) (if (> a b) a b))
 (define (min a b) (if (< a b) a b))