Project

General

Profile

Actions

Bug #5713

closed

Fixnum#** returns Infinity for 0 ** negative Bignum

Added by john_firebaugh (John Firebaugh) over 12 years ago. Updated about 11 years ago.

Status:
Closed
Target version:
ruby -v:
ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin10.8.0]
Backport:
[ruby-core:41494]

Description

=begin
Instead it should raise ZeroDivisionError, the same as negative Fixnums.

wordsize = 8 * 1.size
fixnum_min = -2 ** (wordsize - 2)

def zero_power(exp)
0 ** exp
rescue ZeroDivisionError
"ZeroDivisionError"
end

[-1, fixnum_min, (fixnum_min-1)].each {|i| puts zero_power(i)}
=end


Related issues 1 (0 open1 closed)

Related to Ruby master - Bug #5715: +/-1 ** Bignum returns different results than +/-1 ** FixnumClosedmarcandre (Marc-Andre Lafortune)12/06/2011Actions

Updated by marcandre (Marc-Andre Lafortune) over 12 years ago

  • Assignee set to marcandre (Marc-Andre Lafortune)

Updated by john_firebaugh (John Firebaugh) over 12 years ago

The execution path of 0 ** -Bignum goes to Rational(0) ** -Bignum, so I think the issue is there. I.e. Rational(0) ** -Bignum should raise ZeroDivisionError, the same as Rational(0) ** -Fixnum.

Actions #3

Updated by marcandre (Marc-Andre Lafortune) over 12 years ago

  • Category set to core
  • Target version set to 2.0.0

John Firebaugh wrote:

The execution path of 0 ** -Bignum goes to Rational(0) ** -Bignum, so I think the issue is there. I.e. Rational(0) ** -Bignum should raise ZeroDivisionError, the same as Rational(0) ** -Fixnum.

Yes, unless there is objection, Rational#** should treat 0 and 1 as special cases before resorting to conversion to float, i.e.

Rational(0) ** (-2**100) # => Infinity, should raise an Error
Rational(0) ** (2**100) # => 0.0, should be Rational(0)
Rational(1) ** (2**100) # => 1.0, should be Rational(1)
Actions #5

Updated by shyouhei (Shyouhei Urabe) about 12 years ago

  • Status changed from Open to Assigned
Actions #6

Updated by marcandre (Marc-Andre Lafortune) about 11 years ago

  • Status changed from Assigned to Closed
  • % Done changed from 0 to 100

This issue was solved with changeset r39063.
John, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.


  • rational.c (nurat_expt): Deal with special cases for rationals 0, ±1
    [bug #5713] [bug #5715]
Actions

Also available in: Atom PDF

Like0
Like0Like0Like0Like0Like0Like0