Issue #5715 has been reported by John Firebaugh. ---------------------------------------- Bug #5715: +/-1 ** Bignum returns different results than +/-1 ** Fixnum http://redmine.ruby-lang.org/issues/5715 Author: John Firebaugh Status: Open Priority: Normal Assignee: Category: Target version: ruby -v: ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin10.8.0] =begin Consider (({1 ** expt})) and (({(-1) ** expt})). When ((|expt|)) is a Fixnum, the result is always 1, -1, Rational(1/1), or Rational(-1,1) depending on the signs of the operands and parity of the exponent. When ((|expt|)) is a Bignum, Float 1.0 is always returned. Either the behavior for Fixnum exponents should be followed exactly (preferred), or at the very least -1.0 should be returned when the base is -1 and the exponent is odd. $VERBOSE = nil wordsize = 8 * 1.size fixnum_max = 2 ** (wordsize - 2) - 1 fixnum_min = -2 ** (wordsize - 2) [1, -1].each do |a| [ 1, 2, fixnum_max, fixnum_max + 1, fixnum_max + 2, -1, -2, fixnum_min, fixnum_min - 1, fixnum_min - 2].each do |b| puts "%5s ** %20s (%s) == %5s" % [a, b, b.class, a ** b] end end Output: 1 ** 1 (Fixnum) == 1 1 ** 2 (Fixnum) == 1 1 ** 4611686018427387903 (Fixnum) == 1 1 ** 4611686018427387904 (Bignum) == 1 1 ** 4611686018427387905 (Bignum) == 1 1 ** -1 (Fixnum) == 1/1 1 ** -2 (Fixnum) == 1/1 1 ** -4611686018427387904 (Fixnum) == 1/1 1 ** -4611686018427387905 (Bignum) == 1.0 # Bug 1 ** -4611686018427387906 (Bignum) == 1.0 # Bug -1 ** 1 (Fixnum) == -1 -1 ** 2 (Fixnum) == 1 -1 ** 4611686018427387903 (Fixnum) == -1 -1 ** 4611686018427387904 (Bignum) == 1 -1 ** 4611686018427387905 (Bignum) == -1 -1 ** -1 (Fixnum) == -1/1 -1 ** -2 (Fixnum) == 1/1 -1 ** -4611686018427387904 (Fixnum) == 1/1 -1 ** -4611686018427387905 (Bignum) == 1.0 # Bug -1 ** -4611686018427387906 (Bignum) == 1.0 # Bug =end
on 2011-12-06 05:27
on 2011-12-09 18:01
Issue #5715 has been updated by John Firebaugh. The failing cases are the ones that go through the Rational(+/-1) ** Bignum code path, so this is closely related to #5713. ---------------------------------------- Bug #5715: +/-1 ** Bignum returns different results than +/-1 ** Fixnum http://redmine.ruby-lang.org/issues/5715 Author: John Firebaugh Status: Open Priority: Normal Assignee: Category: Target version: ruby -v: ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin10.8.0] =begin Consider (({1 ** expt})) and (({(-1) ** expt})). When ((|expt|)) is a Fixnum, the result is always 1, -1, Rational(1/1), or Rational(-1,1) depending on the signs of the operands and parity of the exponent. When ((|expt|)) is a Bignum, Float 1.0 is always returned. Either the behavior for Fixnum exponents should be followed exactly (preferred), or at the very least -1.0 should be returned when the base is -1 and the exponent is odd. $VERBOSE = nil wordsize = 8 * 1.size fixnum_max = 2 ** (wordsize - 2) - 1 fixnum_min = -2 ** (wordsize - 2) [1, -1].each do |a| [ 1, 2, fixnum_max, fixnum_max + 1, fixnum_max + 2, -1, -2, fixnum_min, fixnum_min - 1, fixnum_min - 2].each do |b| puts "%5s ** %20s (%s) == %5s" % [a, b, b.class, a ** b] end end Output: 1 ** 1 (Fixnum) == 1 1 ** 2 (Fixnum) == 1 1 ** 4611686018427387903 (Fixnum) == 1 1 ** 4611686018427387904 (Bignum) == 1 1 ** 4611686018427387905 (Bignum) == 1 1 ** -1 (Fixnum) == 1/1 1 ** -2 (Fixnum) == 1/1 1 ** -4611686018427387904 (Fixnum) == 1/1 1 ** -4611686018427387905 (Bignum) == 1.0 # Bug 1 ** -4611686018427387906 (Bignum) == 1.0 # Bug -1 ** 1 (Fixnum) == -1 -1 ** 2 (Fixnum) == 1 -1 ** 4611686018427387903 (Fixnum) == -1 -1 ** 4611686018427387904 (Bignum) == 1 -1 ** 4611686018427387905 (Bignum) == -1 -1 ** -1 (Fixnum) == -1/1 -1 ** -2 (Fixnum) == 1/1 -1 ** -4611686018427387904 (Fixnum) == 1/1 -1 ** -4611686018427387905 (Bignum) == 1.0 # Bug -1 ** -4611686018427387906 (Bignum) == 1.0 # Bug =end
on 2011-12-09 19:45
Issue #5715 has been updated by Marc-Andre Lafortune. Category set to core Assignee set to Marc-Andre Lafortune Just saw this update. Yes, as I stated, same issue as 5713. Yes the case for (-1) and bignum exponents can be fixed too. The case for 1 and 0 must be addressed for rational and float exponents too (but -1 will go to float for those) ---------------------------------------- Bug #5715: +/-1 ** Bignum returns different results than +/-1 ** Fixnum http://redmine.ruby-lang.org/issues/5715 Author: John Firebaugh Status: Open Priority: Normal Assignee: Marc-Andre Lafortune Category: core Target version: ruby -v: ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin10.8.0] =begin Consider (({1 ** expt})) and (({(-1) ** expt})). When ((|expt|)) is a Fixnum, the result is always 1, -1, Rational(1/1), or Rational(-1,1) depending on the signs of the operands and parity of the exponent. When ((|expt|)) is a Bignum, Float 1.0 is always returned. Either the behavior for Fixnum exponents should be followed exactly (preferred), or at the very least -1.0 should be returned when the base is -1 and the exponent is odd. $VERBOSE = nil wordsize = 8 * 1.size fixnum_max = 2 ** (wordsize - 2) - 1 fixnum_min = -2 ** (wordsize - 2) [1, -1].each do |a| [ 1, 2, fixnum_max, fixnum_max + 1, fixnum_max + 2, -1, -2, fixnum_min, fixnum_min - 1, fixnum_min - 2].each do |b| puts "%5s ** %20s (%s) == %5s" % [a, b, b.class, a ** b] end end Output: 1 ** 1 (Fixnum) == 1 1 ** 2 (Fixnum) == 1 1 ** 4611686018427387903 (Fixnum) == 1 1 ** 4611686018427387904 (Bignum) == 1 1 ** 4611686018427387905 (Bignum) == 1 1 ** -1 (Fixnum) == 1/1 1 ** -2 (Fixnum) == 1/1 1 ** -4611686018427387904 (Fixnum) == 1/1 1 ** -4611686018427387905 (Bignum) == 1.0 # Bug 1 ** -4611686018427387906 (Bignum) == 1.0 # Bug -1 ** 1 (Fixnum) == -1 -1 ** 2 (Fixnum) == 1 -1 ** 4611686018427387903 (Fixnum) == -1 -1 ** 4611686018427387904 (Bignum) == 1 -1 ** 4611686018427387905 (Bignum) == -1 -1 ** -1 (Fixnum) == -1/1 -1 ** -2 (Fixnum) == 1/1 -1 ** -4611686018427387904 (Fixnum) == 1/1 -1 ** -4611686018427387905 (Bignum) == 1.0 # Bug -1 ** -4611686018427387906 (Bignum) == 1.0 # Bug =end
on 2013-01-25 06:47
Issue #5715 has been updated by marcandre (Marc-Andre Lafortune). Target version set to 2.0.0 ---------------------------------------- Bug #5715: +/-1 ** Bignum returns different results than +/-1 ** Fixnum https://bugs.ruby-lang.org/issues/5715#change-35620 Author: john_firebaugh (John Firebaugh) Status: Assigned Priority: Normal Assignee: marcandre (Marc-Andre Lafortune) Category: core Target version: 2.0.0 ruby -v: ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin10.8.0] =begin Consider (({1 ** expt})) and (({(-1) ** expt})). When ((|expt|)) is a Fixnum, the result is always 1, -1, Rational(1/1), or Rational(-1,1) depending on the signs of the operands and parity of the exponent. When ((|expt|)) is a Bignum, Float 1.0 is always returned. Either the behavior for Fixnum exponents should be followed exactly (preferred), or at the very least -1.0 should be returned when the base is -1 and the exponent is odd. $VERBOSE = nil wordsize = 8 * 1.size fixnum_max = 2 ** (wordsize - 2) - 1 fixnum_min = -2 ** (wordsize - 2) [1, -1].each do |a| [ 1, 2, fixnum_max, fixnum_max + 1, fixnum_max + 2, -1, -2, fixnum_min, fixnum_min - 1, fixnum_min - 2].each do |b| puts "%5s ** %20s (%s) == %5s" % [a, b, b.class, a ** b] end end Output: 1 ** 1 (Fixnum) == 1 1 ** 2 (Fixnum) == 1 1 ** 4611686018427387903 (Fixnum) == 1 1 ** 4611686018427387904 (Bignum) == 1 1 ** 4611686018427387905 (Bignum) == 1 1 ** -1 (Fixnum) == 1/1 1 ** -2 (Fixnum) == 1/1 1 ** -4611686018427387904 (Fixnum) == 1/1 1 ** -4611686018427387905 (Bignum) == 1.0 # Bug 1 ** -4611686018427387906 (Bignum) == 1.0 # Bug -1 ** 1 (Fixnum) == -1 -1 ** 2 (Fixnum) == 1 -1 ** 4611686018427387903 (Fixnum) == -1 -1 ** 4611686018427387904 (Bignum) == 1 -1 ** 4611686018427387905 (Bignum) == -1 -1 ** -1 (Fixnum) == -1/1 -1 ** -2 (Fixnum) == 1/1 -1 ** -4611686018427387904 (Fixnum) == 1/1 -1 ** -4611686018427387905 (Bignum) == 1.0 # Bug -1 ** -4611686018427387906 (Bignum) == 1.0 # Bug =end
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