From: "Derrick B." <lists@...>
Date: 2012-12-21T13:59:41+09:00
Subject: Re: Perl to Ruby: regex captures to assignment.

7stud -- wrote in post #1089755:
>    %r{
>         (
>           [-]?
>           \d+
>         )?
>         \s*
>         (\d+)
>         /
>         (\d+)
>      }xms
>   )
>

That works, but it needs another "[-]?" in the second group to handle
negative numerators, or whole numbers:

%r#(?:([-]?\d+) )??([-]?\d+)/(\d+)#xms

...but I should probably add the "\s*" and not expect a single space.  I
got the "??" from Perl, but it seems to not be a problem in Ruby.

Lastly, my code I posted did not convert terms to improper fractions,
correctly.  Here is the code that works:

Ruby:
    n = ( w == w.abs ) ?
        n + w * d :
        -1 * ( n - w * d ) if d != 0  # to negative improper fraction

Perl:
    $n = ( $w == abs($w) )
        ? $n + $w * $d                  # to positive improper fraction
        : -1 * ( $n - $w * $d ) if $d;  # to negative improper fraction

...which leads me to another question:

Why is it that when I try to add
a comment after a line continuation backslash, Ruby says:

./ratnum.rb:14: syntax error, unexpected $undefined
    n = ( w == w.abs ) ? \ #
                          ^
./ratnum.rb:15: syntax error, unexpected ':', expecting keyword_end

Ruby should respect my need for comments!  :)

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