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

Browse source 
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
This commit is contained in:
matz 2007-07-16 15:56:16 +00:00
parent 8c3546c744
commit 217db90e87
3 changed files with 45 additions and 6 deletions
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8
ChangeLog
View file

@ -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

41
numeric.c
View file

@ -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);
}
}
/*

2
test/ruby/test_fixnum.rb
View file

@ -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