From: Maurice Codik <maurice.codik@...>
Date: 2006-02-08T09:54:03+09:00
Subject: Re: Meta-Meta-Programming

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Yet another suggestion-- I wrote a little library that lets you define
simple contracts for function inputs... useful if you dont want to repeat
the same duck-type assertions over and over again.

here's an example of how it works:

require "contracts"
class TestContracts
  extend Contracts

  define_data :writable =3D> lambda {|x| x.respond_to?("write") and
x.respond_to?("closed?") and not x.closed? },
              :positive =3D> lambda {|x| x >=3D 0 }

  contract :hello, [:positive, :string, :writable]

  def hello(n, s, f)
    n.times { f.write "hello #{s}!\n" }
  end
end

tc =3D TestContracts.new
tc.hello(2, "world", $stdout)
# -> hello world!
# -> hello world!

# tc.hello(2, 3, $stdout)
#  -> test-contracts.rb:22: argument 2 of method 'hello' must satisfy
the 'string' contract (Contracts::ContractViolation)

You can download it at: : http://mauricecodik.com/projects/ruby/contracts.r=
b

Maurice

On 2/7/06, Trans <transfire@gmail.com> wrote:
>
> > So I have to replace every Foo.new to JustWrap.new, just to
> > activate the debugging? Kidding?
>
> No you do not. A cut is a _transparent_ class. You would still use
> Foo.new.
>
> T.
>
>
>

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