From: Wilson Bilkovich <wilsonb@...>
Date: 2006-02-12T12:28:39+09:00
Subject: Re: Scanning a string for decimal numbers

Well, that's what I get for dashing off a quick e-mail before dinner. 
The last problem Alexis mentioned is caused by the overly-specific
lookahead at the end.  Here's a version that fixes that:

irb(main):013:0> a = '24.5 + 24 + 24. + 24.4.'
=> "24.5 + 24 + 24. + 24.4."
irb(main):014:0> a.scan /[-+]?(\d+(?:\.\d+)?)(?=[^\d])/
=> [["24.5"], ["24"], ["24"], ["24.4"]]
irb(main):015:0>

One of the characters '-' or '+', optionally
Followed by at least one digit.
Followed by an optional group containing a period, and one or more digits.
The capturing group ends when the next character is something other
than a digit.

The (?:) mess is there so that '24.' doesn't end up with the period on the end.

On 2/11/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:
> Seems I accidently got my text marked as a qoute in my last mail, so I'll
> just send it a again:
>
> Let me see if I got it right then. I'll like to use periods only for my
> decimal numbers. I also need normal integers so 24. being accepted won't
> matter. Will this fix the problems you presented?:
> /[-+]?(\d+\.?\d*)(?=\s|$)/
>
>
> I don't know if it takes care of the last problem, because I didn't
> understand it.
>
>
> 2006/2/12, Jeppe Jakobsen <jeppe88@gmail.com>:
> >
> > 2006/2/12, Alexis Reigel <mail@koffeinfrei.org>:
> > >
> > > >
> > > > This should handle periods or commas as the separator.
> > > >
> > > > a = "24,4 + 55,2 + 55 - 44,0"
> > > >    => "24,4 + 55,2 + 55 - 44,0"
> > > > a.scan /(\d+,?.?\d*)(?=\s|$)/
> > > >    => [["24,4"], ["55,2"], ["55"], ["44,0"]]
> > > >
> > >
> > > Some problems here:
> > > - signs are disregarded ("-24,4" becomes "24,4")
> > > - Invalid numbers are accepted: eg. "24,.4" "24,." "24." "24,"
> > > - "." should be escaped. As you used it here, it means "any character"
> > > (except newline), so many invalid numbers are accepted (e.g. "24w"...)
> > > - If something different from whitespace follows the number, it is not
> > > or false accepted, e.g. "24.4." becomes "4." instead of "24.4"
> > > - ...
> > >
> > >
> > > Alexis.
> >
> >
>
>