Bug #5713

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

Added by john_firebaugh (John Firebaugh) 6 months ago. Updated 2 months ago.

[ruby-core:41494]
Status:Assigned Start date:12/06/2011
Priority:Normal Due date:
Assignee:marcandre (Marc-Andre Lafortune) % Done:

0%
Category:core
Target version:2.0.0
ruby -v:ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin10.8.0]

Description

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)}

Related issues

related to ruby-trunk - Bug #5715: +/-1 ** Bignum returns different results than +/-1 ** Fixnum Assigned 12/06/2011

History

[ruby-core:41553]#1
Updated by marcandre (Marc-Andre Lafortune) 6 months ago

  • Assignee set to marcandre (Marc-Andre Lafortune)

[ruby-core:41571]#2
Updated by john_firebaugh (John Firebaugh) 6 months 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.

#3
Updated by marcandre (Marc-Andre Lafortune) 6 months 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)

#5
Updated by shyouhei (Shyouhei Urabe) 2 months ago

  • Status changed from Open to Assigned

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