diff options
author | matz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 2007-07-16 15:56:16 +0000 |
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committer | matz <matz@b2dd03c8-39d4-4d8f-98ff-823fe69b080e> | 2007-07-16 15:56:16 +0000 |
commit | 217db90e8705162bef4428c7d608a7d6fdf18b2a (patch) | |
tree | 84d1a784ac4b2ca0b0249a2db5431ad7ede46624 /numeric.c | |
parent | 8c3546c7441897721453866342828d91aba63b32 (diff) |
* 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
Diffstat (limited to 'numeric.c')
-rw-r--r-- | numeric.c | 41 |
1 files changed, 36 insertions, 5 deletions
@@ -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); + } } /* |