* 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

ChangeLog

@@ -1,3 +1,11 @@
+Sat Jul 14 22:49:30 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* 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.
+
 Sat Jul 14 18:46:35 2007  Tanaka Akira  <akr@fsij.org>
 
 	* configure.in: add --with-valgrind.

numeric.c

@@ -2326,14 +2326,21 @@ int_pow(long x, unsigned long y)
 static VALUE
 fix_pow(VALUE x, VALUE y)
 {
-    if (FIXNUM_P(y)) {
-	long a, b;
+    long a = FIX2LONG(x);
+
+    if (FIXNUM_P(y)) {
+	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);
     }

test/ruby/test_fixnum.rb

@@ -12,7 +12,7 @@ class TestFixnum < Test::Unit::TestCase
 
   def test_pow
     [1, 2, 2**64, 2**63*3, 2**64*3].each do |y|
-      [1, 3].each do |x|
+      [-1, 0, 1].each do |x|
         z1 = x**y
         z2 = (-x)**y
         if y % 2 == 1