From: Caleb Clausen <vikkous@...>
Date: 2010-08-12T00:18:08+09:00
Subject: Re: "NaN".to_f revisited

On 8/11/10, Brian Candler <b.candler@pobox.com> wrote:
> Might give some strange behaviour though:
>
> "1$".to_f             => 1.0
> "nonsense".to_f       => 0.0
> "nanotubes".to_f      => Nan ?
> "inferiority".to_f    => Inf ?

Normally if the string starts with non-numeric characters, converting
to numbers yields a zero result. This is to remain consistent with
atof and strtod from the standard c library. On my machine, the man
page for strtod contains this paragraph:

     Alternatively, if the portion of the string following the optional plus
     or minus sign begins with ``INFINITY'' or ``NAN'', ignoring case, it is
     interpreted as an infinity or a quiet NaN, respectively.

In practice, strtod seems to actually recognize INF rather than the
fully-spelled-out INFINITY as the trigger for returning infinity. So,
your last 2 examples would return NaN and Inf if passed to strtod.