* numeric.c (fix_pow): integer power calculation: 0**n => 0,

  1**n => 1, -1**n => 1 (n: even) / -1 (n: odd).

* test/ruby/test_fixnum.rb (TestFixnum::test_pow): update test
  suite.  pow(-3, 2^64) gives NaN when pow(3, 2^64) gives Inf.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@12789 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 19 insertions, 4 deletions

diff --git a/numeric.c b/numeric.c
index a50199dce3..9f986a7633 100644
--- a/numeric.c
+++ b/numeric.c
@@ -2326,14 +2326,21 @@ int_pow(long x, unsigned long y)
 static VALUE
 fix_pow(VALUE x, VALUE y)
 {
+    long a = FIX2LONG(x);
+
     if (FIXNUM_P(y)) {
-	long a, b;
+	long b = FIX2LONG(y);
 
-	b = FIX2LONG(y);
 	if (b == 0) return INT2FIX(1);
 	if (b == 1) return x;
-	a = FIX2LONG(x);
 	if (a == 0) return INT2FIX(0);
+	if (a == 1) return INT2FIX(1);
+	if (a == -1) {
+	    if (b % 2 == 0)
+		return INT2FIX(1);
+	    else 
+		return INT2FIX(-1);
+	}
 	if (b > 0) {
 	    return int_pow(a, b);
 	}
@@ -2341,10 +2348,18 @@ fix_pow(VALUE x, VALUE y)
     }
     switch (TYPE(y)) {
       case T_BIGNUM:
+	if (a == 0) return INT2FIX(0);
+	if (a == 1) return INT2FIX(1);
+	if (a == -1) {
+	    if (int_even_p(y)) return INT2FIX(1);
+	    else return INT2FIX(-1);
+	}
 	x = rb_int2big(FIX2LONG(x));
 	return rb_big_pow(x, y);
       case T_FLOAT:
-	return rb_float_new(pow((double)FIX2LONG(x), RFLOAT(y)->value));
+	if (a == 0) return rb_float_new(0.0);
+	if (a == 1) return rb_float_new(1.0);
+	return rb_float_new(pow((double)a, RFLOAT(y)->value));
       default:
 	return rb_num_coerce_bin(x, y);
     }