Bug #11995: BigDecimal#power fails for some values

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-linux]
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN

[dolzenko (Evgeniy Dolzhenko)]

$ irb -rbigdecimal

BigDecimal('-0.5').power(BigDecimal('0.2'))
Math::DomainError: Zero or negative argument for log

but

-0.5**0.2
=> -0.8705505632961241

The same is true for a few other exponent version I have tested. Is that feature or bug?

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Rejected

The latter is parsed as -(0.5**0.2).

$ ruby -e 'p (-0.5)**0.2'
(0.7042902001692478+0.5116967824803669i)

Float#** can result an imaginary number, but BigDecimal is only for real numbers.