fix lcm on 0

svn: r11194

collects/scribblings/reference/numbers.scrbl

@@ -291,15 +291,17 @@ otherwise.}
 
 
 @defproc[(gcd [n integer?] ...) integer?]{ Returns the
- @as-index{greatest common divisor} of the @scheme[n]s. If no
- arguments are provided, the result is @scheme[0].
+ @as-index{greatest common divisor} (a non-negative number) of the
+ @scheme[n]s. If no arguments are provided, the result is
+ @scheme[0]. If all arguments are zero, the result is zero.
 
 @examples[(gcd 10) (gcd 12 81.0)]}
 
 
-@defproc[(lcm [n integer?] ...) integer?]{ Returns the
- @as-index{least common multiple} of the @scheme[n]s. If no arguments
- are provided, the result is @scheme[1].
+@defproc[(lcm [n integer?] ...) integer?]{ Returns the @as-index{least
+ common multiple} (a non-negative number) of the @scheme[n]s. If no
+ arguments are provided, the result is @scheme[1]. If any argument is
+ zero, the result is zero.
 
 @examples[(lcm 10) (lcm 3 4.0)]}
 

collects/tests/mzscheme/number.ss

@@ -1119,6 +1119,9 @@
 (test 5.0 gcd 5.0 -10)
 (test 5.0 gcd 5.0)
 (test 5.0 gcd -5.0)
+(test 3 gcd 0 0 3 0)
+(test 3.0 gcd 0.0 0 3 0)
+(test 0 gcd 0 0 0)
 (err/rt-test (gcd 5.0+0.0i 10))
 (err/rt-test (gcd 5.0 10+0.0i))
 (test (expt 3 37) gcd (expt 9 35) (expt 6 37))
@@ -1140,6 +1143,9 @@
 (test 5 lcm 5)
 (test 5 lcm -5)
 (test 0 lcm 123 0)
+(test 0 lcm 0 0)
+(test 0.0 lcm 0 0.0)
+(test 0.0 lcm 0.0 0)
 (test 30.0 lcm 5 6.0)
 (test 6.0 lcm 6.0)
 (test 6.0 lcm -6.0)

src/mzscheme/src/number.c

@@ -1086,6 +1086,9 @@ bin_lcm (Scheme_Object *n1, Scheme_Object *n2)
   Scheme_Object *d, *ret;
 
   d = scheme_bin_gcd(n1, n2);
+
+  if (scheme_is_zero(d))
+    return d;
   
   ret = scheme_bin_mult(n1, scheme_bin_quotient(n2, d));