From: William James <w_a_x_man@...>
Date: 2007-10-02T21:50:11+09:00
Subject: Re: help in my own gsub design..

On Oct 2, 6:35 am, Josselin <josse...@wanadoo.fr> wrote:
> I don't use it very often, rather copying from example, but it's so
> useful that I should learn how to write it
> I'd appreciate any guru tip on how to proceed once the problem is on
> the paper :
>
> example :
>
> INPUT STRINGS
>
> 1-  input can contains spaces (should be eliminated)
>
> 2- good patterns :
>
> 2a- an Integer  like 99  (no limit)
> a   >   >=  <  <=   <>  !=   followed by an Integer      like   >99
>
> >=99  <99  <=99  <>99   !=99
>
> 2b- a String like:    abcd  abc99  99abc  a99bc
>
> 2c- a  % sign  followed by a String
>         like  %abcd  %abc99  %99abc  %a99bc %abcd
>
> 2d- a    String  followed by a  % sign
>         like  abcd%  abc99%  99abc%  a99bc%
>
> 2e- a String leading containing or ending with, one or many * sign(s)
>         like  a*bcd  a**bc99  99*a*bc  *a99bc a99bc*  *a99bc*     *a9**9b*c*
>
> 3-any other pattern will be considered as wrong
>
> OUTPUTS
>
> 2a ->   an array [characters, Integer]    like   [ "<>", 99]
> 2b, 2c, 2d,2e  ->  an array [ nil, String]  like  [nil, abcd]  or [nil,
> %abcd] or [nil, a99bc%] or [nil, *a9**9b*c]
>
> I am interesting in understanding the design process... : how should I
> start when designing such gsub routine ?
> should I state it differently on paper first ?  well, any tip that can
> help me to build the next ones....
>
> thanks for your support
>
> joss

def foo s
  case s
    when /^(>|>=|<|<=|<>|!=)?(\d+)$/
      [ $1 || "", $2.to_i ]
    when /^(%)?[a-z\d]+(%)?$/
      return nil  if 1 != $~.captures.compact.size
      [ nil, $& ]
    when /^(?=.*\*)[*a-z\d]+$/
      [ nil, $& ]
  end
end

p foo( "88" )
p foo( "<>88" )
p foo( "%33" )
p foo( "33%" )
p foo( "a*9" )
p foo( 'bat' )