From: Florian Gross <flgr@...>
Date: 2005-02-17T06:19:50+09:00
Subject: Re: DesignByContract (was RE: utilizing ++ and -- for comments)

Pe�a, Botp wrote:

> at [mailto:"neo.matrix.fr(at)"@wanadoo.fr] wrote:
> 
> // > The closest connection bw code and comments I can think of 
> //is (eiffel's)  > pre/post condition.. if fully agree with you 
> //and I believe at 100% in pre/post conditions, 
> //class invariant, check clause... and in general in Design By Contract
> //
> //it answers well at the question : Who do what ? With wich 
> //garanties ? == The *most* important question to solve the 
> //issue of the quality of 
> //software ==
> 
> if memory serves me right (my mem misses many times :), I think Andy Hunt
> started implementing something like this. I searched in raa but (sadly)
> cannot find one though :(

Yup, it's a bit out-dated, though. I'll have a look at integrating 
Eiffel-style DBC (pre and post-checks plus invariants) with 
ruby-contract (see http://ruby-contract.rubyforge.org/) based on Andy's 
code soon, though.

I think I'll use an interface like this:

class MyArray
   def pop() ... end

   check :pop, :pre do
     size > 0
   end

   check :pop, :post do # couldn't think of a better sample here
     size >= 0
   end

   check :invariant do
     size >= 0
   end
end

I'm not sure about using "check" though -- I think that is to close to 
type / signature checking which I already have implemented.

If any of you happens to have any alternative suggestions, feel free to 
share them!