From: Ken Coar <the.rodent.of.unusual.size@...>
Date: 2010-02-22T18:38:34+09:00
Subject: Re: Complex type-checking

Robert Klemme wrote:
> 
>> So please
>> let's leave the 'why do you want to do that' bit alone for now. :-)
> 
> Sorry, I can't.  Why do you want to do that? :-)

:-)

>> Which is actually turning out to be a right bugger to code, actually.
> 
> Is it?

Well, it seems to be..

The thing is, the Point class match works all right -- but when 
specified as individual coordinates, they can be integers (potentially 
bignums) or floats -- so checking the actual coordinates is not as 
simple as matching the class.  I *could* do a (Fixnum|Float|...) 
alternation, I suppose, but that doesn't extend to cases in which 
someone might be using a custom class extending one of those.  Which is 
actually probably a bit unlikely, so maybe I'll just rule that 
possibility out. :-)

> def pattern_check(args, pattern)
>   m = pattern.match(args.map{|x|x.class}.join(' '))
> 
>   if m
>     m.to_a.each_with_index do |m,i|
>       return i if i > 0 && m
>     end
>   end
> 
>   raise ArgumentError, args.inspect
> end
> 
> def m(*a)
>   case pattern_check(a, %r{\A(?:(String String)|(Fixnum))\z})
>   when 1
>     printf "Two strings: %p\n", a
>   when 2
>     printf "A number: %p\n", a
>   else
>     raise ArgumentError, a.inspect
>   end
> end
> 
> Method m does look ugly though.

Consider also that the argument list may include more than one tuple..

This has given me some ideas, though.  Thanks!

#ken B-)}
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