From: Markus <markus@...>
Date: 2004-10-13T01:14:30+09:00
Subject: Re: "nan".to_f ?


     Yes, but his point is that "NaN" _is_ the string representation of
valid floating point value, defined and handled by the system, with
standardized semantics, etc.   
    "NaN".to_f should return NaN.  How else are you going to reliably
get NaN if you need it?
    IMO, this is a bug.

     -- Markus


On Tue, 2004-10-12 at 02:39, Stephan K辰mper wrote:
> Hi Thomas, hi Rubyists
> 
> Thomas Fini Hansen wrote:
> 
> > ---
> > irb(main):001:0> VERSION
> > "1.6.7"
> > irb(main):002:0> "nan".to_f
> > NaN
> > ---
> > irb(main):001:0> VERSION
> > => "1.8.2"
> > irb(main):002:0> "nan".to_f
> > => 0.0
> > ---
> > 
> > (1.8.2 is really 1.8.1+1.8.2pre2-1woody1 in Debian)
> > 
> > I wouldn't have been surprised if it was the other way round. Can
> > anyone explain why it is so? Seemed like a nice feature to me.
> > 
> 
>  >ri String#to_f
> ------------------------------------------------------------ String#to_f
>       str.to_f   => float
> ------------------------------------------------------------------------
>       Returns the result of interpreting leading characters in _str_ as a
>       floating point number. Extraneous characters past the end of a
>       valid number are ignored. If there is not a valid number at the
>       start of _str_, +0.0+ is returned. This method never raises an
>       exception.
> 
>          "123.45e1".to_f        #=> 1234.5
> 
>          "45.67 degrees".to_f   #=> 45.67
> 
>          "thx1138".to_f         #=> 0.0
> 
> I don't use String#to_f a lot, because I'd prefer Float( a_string ).
> Float() is stricter and raises an ArgumentError if the whole String 
> can't be interpreted as a Float, while String#to_s tries to create a 
> Float from the first characters and stops when/if there are any chars 
> that wouldn't yield a Float.
> 
> Happy rubying
> 
> Stephan