From: Fleck Jean-Julien <jeanjulien.fleck@...>
Date: 2009-12-19T01:05:41+09:00
Subject: Re: Math errors

Hello,

> This behavior was shown in ruby ree 1.8.6, 1.8.6, 1.8.7, 1.9.1
>
> -27**1/3.0       => -9.0
> -27 ** 1/3.0     => -9.0
> -27 ** (1/3.0)   => -3.0
> -27**(1/3.0)     => -3.0
> (-27)**(1/3.0)   => NaN
> (-27) ** (1/3.0) => NaN
>
> OK, the first two expression are evaluated as (-27**1)/3 => -9
> The second two are correct (what I expected).
> But the last two, WHY??

As Matz said, the second two are evaluated as - (27**(1/3.0)), that is
you take the cubic root of +27 which is 3 and then distribute the
minus.
That way, you take the cubic root of a positive number which does not
raise any problem.

Cheers,

-- 
JJ Fleck
PCSI1 Lycée Kléber