Re: [boost] [contract] Contract Programming Library

Subject: Re: [boost] [contract] Contract Programming Library
From: Lorenzo Caminiti (lorcaminiti_at_[hidden])
Date: 2010-01-05 21:58:53

Vicente:

> Have you considered to add block invariants? Maybe you can complete the table Contract Programming Feature Comparison.

I think block invariants could be added if there was interest. Indeed,
I have already implemented a class for Eiffel-like loop-contract with
both invariants and variants (but I never use it in real code).

In the Contract Programming proposal for the C++ standard, block
invariants are interesting also because they allow for additional
compiler optimization but this benefit does not apply to a library.

> If I have understood your library require the type is CopyConstructible to manage with postconditions. Have you considered to relax this constraint?

Yes, the library requires that a type T is ConstantCopyConstructible
in order for a variable of such a type to have old value in
postconditions. However, this constraint only applies for a type T
tagged copyable by programmers by copyable<T>. Therefore, if T is not
ConstantCopyConstructible, or simply if its old value is not needed in
postconditions, programmers do not tag T copyable and the library does
not add any constraint on T (plus there is no extra copy overhead for
old).

ConstantCopyConstructible is same as the CopyConstructible concept but
the copy constructor must operate on a *const* source object "T::T(T
const& source)".

Regards,
Lorenzo