[boost] Re: Proposal: Design by Contract / Pre & Postconditions library

From: Larry Evans (cppljevans_at_[hidden])
Date: 2005-04-17 08:23:20

On 04/17/2005 08:56 AM, Yariv Tal wrote:
> Is there a need for a Design by Contract (a.k.a Pre & Post conditions)
> library?
Sure!

[snip]
> Unlike many other such libraries it allows for defining all condition
> types at the begining of the method, instead of making you define the
> "post" checks just before method exit (which usually constrains you
> to a single-point-of-method-exit design).
> 
> See EXAMPLES below.
> 
> Here's a quick summary of condition types:
> 
> - Pre conditions - tested immidiately
> 
> - Post conditions - tested on exiting the method normally (not due to
>      an exception). You can use both "pre"(=old) values and "post"
>      (=current) values in the test expression (i.e.
>      "pre(size) < post(size)").
>      If the method returns a value then you can also, with some work on
>      your part, test against it (i.e. "retval > 0").
> 
> - Exceptional conditions - tested on exiting the method due to an
>      exception. You can use both "pre" and "post" values in the test
>      expression.
> 
> - Delayed Assert - this is just a small add-on that allows you to
>      seperate between an assert's definition time and testing time.
>      It's useful when an assert needs to compare some new value to an
>      "old" value (usually solved by saving the old value in a temp
>      variable, which I find messy).
> 

Sounds great to me.