From 217db90e8705162bef4428c7d608a7d6fdf18b2a Mon Sep 17 00:00:00 2001
From: matz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Mon, 16 Jul 2007 15:56:16 +0000
Subject: * 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/branches/ruby_1_8@12808 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog                |  8 ++++++++
 numeric.c                | 41 ++++++++++++++++++++++++++++++++++++-----
 test/ruby/test_fixnum.rb |  2 +-
 3 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index a34fc39305..72016ca4dd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Tue Jul 17 00:50:53 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.
+
 Mon Jul 16 23:07:51 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* lib/base64.rb (Base64::b64encode): should not specify /o option
diff --git a/numeric.c b/numeric.c
index 1f306df657..0665314592 100644
--- a/numeric.c
+++ b/numeric.c
@@ -2218,6 +2218,15 @@ int_pow(x, y)
     return LONG2NUM(z);
 }
 
+static VALUE
+int_even_p(VALUE num)
+{
+    if (rb_funcall(num, '%', 1, INT2FIX(2)) == INT2FIX(0)) {
+	return Qtrue;
+    }
+    return Qfalse;
+}
+
 /*
  *  call-seq:
  *    fix ** other         => Numeric
@@ -2234,23 +2243,45 @@ static VALUE
 fix_pow(x, y)
     VALUE x, y;
 {
+    long a = FIX2LONG(x);
+
     if (FIXNUM_P(y)) {
-	long a, b;
+	long b;
 
 	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);
 	}
 	return rb_float_new(pow((double)a, (double)b));
-    } else if (TYPE(y) == T_FLOAT) {
-        long a = FIX2LONG(x);
-        return rb_float_new(pow((double)a, RFLOAT(y)->value));
     }
-    return rb_num_coerce_bin(x, 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:
+	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);
+    }
 }
 
 /*
diff --git a/test/ruby/test_fixnum.rb b/test/ruby/test_fixnum.rb
index 57999d4b03..d17b1f8d49 100644
--- a/test/ruby/test_fixnum.rb
+++ b/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
-- 
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