Forum: Ruby-core [ruby-trunk - Bug #7682][Open] Inconsistent results when using variables versus raw floats in expone

415fb73080f1d9f0922c80153f8e95a6?d=identicon&s=25 ccashwell (Chris Cashwell) (Guest)
on 2013-01-10 21:51
(Received via mailing list)
Issue #7682 has been reported by ccashwell (Chris Cashwell).

----------------------------------------
Bug #7682: Inconsistent results when using variables versus raw floats
in exponential calculations
https://bugs.ruby-lang.org/issues/7682

Author: ccashwell (Chris Cashwell)
Status: Open
Priority: Normal
Assignee:
Category:
Target version: 1.9.3
ruby -v: ruby 1.9.3p194 (2012-04-20 revision 35410)
[x86_64-darwin11.4.0]


When performing exponential calculations using a negative number as the
base, inconsistent results are returned when using the raw value as
opposed to a variable containing the value.

In IRB:

1.9.3p194 :001 > -4.5 ** 0.5
 => -2.1213203435596424
1.9.3p194 :002 > foo = -4.5
 => -4.5
1.9.3p194 :003 > foo ** 0.5
 => (1.2989340843532398e-16+2.1213203435596424i)

The expected behavior is that these two calculations should be
equivalent. The compiler treats the - sign differently when using an
inline float versus a variable float.
Bcb6acc9d0d9bef99e033b36c3d32ca9?d=identicon&s=25 charliesome (Charlie Somerville) (Guest)
on 2013-01-10 22:24
(Received via mailing list)
Issue #7682 has been updated by charliesome (Charlie Somerville).

Status changed from Open to Rejected

=begin
The (({**})) operator has a higher precedence than unary minus, so your
example is actually (({-(4.5 ** 0.5)})).
=end
----------------------------------------
Bug #7682: Inconsistent results when using variables versus raw floats
in exponential calculations
https://bugs.ruby-lang.org/issues/7682#change-35336

Author: ccashwell (Chris Cashwell)
Status: Rejected
Priority: Normal
Assignee:
Category:
Target version: 1.9.3
ruby -v: ruby 1.9.3p194 (2012-04-20 revision 35410)
[x86_64-darwin11.4.0]


When performing exponential calculations using a negative number as the
base, inconsistent results are returned when using the raw value as
opposed to a variable containing the value.

In IRB:

1.9.3p194 :001 > -4.5 ** 0.5
 => -2.1213203435596424
1.9.3p194 :002 > foo = -4.5
 => -4.5
1.9.3p194 :003 > foo ** 0.5
 => (1.2989340843532398e-16+2.1213203435596424i)

The expected behavior is that these two calculations should be
equivalent. The compiler treats the - sign differently when using an
inline float versus a variable float.
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