Re: [boost] Re: STL containers with contracts, any interest?

From: christopher diggins (cdiggins_at_[hidden])
Date: 2005-02-23 11:01:36

----- Original Message ----- 
From: "Yariv Tal" <yariv_tal2003_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Wednesday, February 23, 2005 9:05 AM
Subject: [boost] Re: STL containers with contracts, any interest?

> You may want to take a look at a small DbC library I'm working on called
> ensure++.
>
> You can find it on sourceforge, at http://sourceforge.net/projects/ensure/
>
> It allows you to write the post() part conditions at the _beginning_ of 
> your
> method, near the pre conditions.
> Quick example: (note that I already have a plan on how to remove the need
> for the CONDITIONS, BODY & ENDBODY macros. Software is a constant process 
> of
> improvement :)   )
>
> void push_back(const T& x)  {
>      CONDITIONS
>            ENSURE(!post(&vector_contract::empty, this));
>            ENSURE(post(&vector_contract::size, this) == size() + 1);
>             // let's ensure (some of) the strong exception guarenttee -
>             //no change in size in case of exception
>            EXCEPTIONAL(post(&vector_contract::size, this) == size());
>      BODY
>            inherited::push_back(x);
>      ENDBODY
> }
>
> void pop_back() {
>
>      CONDITIONS
>            REQUIRE(!empty());
>            ENSURE(post(&vector_contract::size, this) == size() - 1);
>             // let's ensure (some of) the strong exception guarenttee -
>             //no change in size in case of exception
>            EXCEPTIONAL(post(&vector_contract::size, this) == size());
>      BODY
>            inherited::pop_back();
>      ENDBODY
> }
>
> [I'm writing this example on the fly - so don't kill me if it doesn't 
> quite
> compile after you download the lib]

Hi Yariv,

This appears to be very cool code. However, I am at a loss to find a good 
reason I would want to place post-conditions at the beginning of a code 
block given that the contract classes are always one-liners (e.g. 
inherited::fxn() ). Any comments?

The EXCEPTIONAL(...) macro is a very good idea which I overlooked, and will 
be borrowing ;-)

Concerning:
> ENSURE(post(&vector_contract::size, this) == size() - 1);

If I understand this correctly, the "vector_contract::" is superflous is it 
not?

Thanks for sharing this with us!

Christopher Diggins
Object Oriented Template Library (OOTL)
http://www.ootl.org