On Solaris, Rational#** returns -Infinity for Rational(0) when passed a negative Float
Rational(0, 1) ** -1.0
=> +Infinity on most platforms, -Infinity on Solaris by default.
The Rational is implicitly converted to the Float value 0.0, and the libm function pow(0.0, -1.0) is called.
Should this kind of behavior be made consistent by Ruby or should we accept this as dependent on the libm/libc used?
They are likely other edges cases for pow() which might differ, and I think in general
Ruby should try to unify these cases so the behavior is consistent across platforms at least for arithmetic.
For more details, please see https://github.com/ruby/rubyspec/issues/134 reported by ngoto.
Updated by ngoto (Naohisa Goto) about 5 years ago
Does 0.0 ** -1 return -Infinity too?
Yes, with default compiler option.
On Solaris, the 0.0 ** -1 could return 3 different values depending on compile-time options: 0, -Infinity, +Infinity.
See below for list of corner-case variations of numerical calculations.
It isn't a problem?
I don't know.