From: Ken Coar <the.rodent.of.unusual.size@...>
Date: 2010-02-22T12:43:19+09:00
Subject: Complex type-checking

I have a number of methods that can take arguments in two different
forms.  As an example:

method(tuple [, ...])

where 'tuple' can be things like (Point, Point, Integer) or (Numeric,
Numeric, Numeric, Numeric, Integer) (so either a Point object
representing the coordinates, or the coordinates directly).

I realise that type-checking in Ruby is anathematic to some, but I want
to generate some intelligent error messages in some cases.  So please
let's leave the 'why do you want to do that' bit alone for now. :-)

One meta-thought I had was for the argument vetter to be passed the
arglist and an array of allowed patterns, like

[
  %r/^(?:(?:Point\s*){2}\s*Integer)+$/,
  %r/^(?:(?:Numeric\s*){4}\s*Integer)+$/
]

and check each tuple by doing kind_of?() of each element against the
appropriate words in the pattern.

Which is actually turning out to be a right bugger to code, actually.

So I'm figuring maybe someone could suggest a better method to me?

Thanks!
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