Re: [boost] [contract] syntax redesign

Subject: Re: [boost] [contract] syntax redesign
From: lcaminiti (lorcaminiti_at_[hidden])
Date: 2011-09-27 11:43:18

lcaminiti wrote:
> 
> After a long time of inactivity for Boost.Contract, I am considering
> how to re-design its macro syntax to make it simpler.
> 

Hello all,

Playing with pp a bit more I realized this alternative syntax is also
possible:

CONTRACT_CLASS( // option A
template( typename T )
class (vector)
) {
    CONTRACT_CLASS_INVARIANT(
        assert(empty() == (size() == 0)) // no trailing `,` or `;` etc
        assert(size() <= capacity)
    )
    
public:
    CONTRACT_FUNCTION_TPL(
    public void (push_back) ( (const T&) value )
        precondition(
            assert(size() < max_size())
        )
        postcondition(
            var(auto old_size = CONTRACT_OLDOF size())
            var(auto old_capacity = CONTRACT_OLDOF capacity())
            assert(back() == val) requires(boost::has_equal_to<T>::value)
            assert(size() == old_size + 1)
            assert(capacity() >= old_capacity)
            const_assert(x, y, x == y)
            static_assert(sizeof(T) >= sizeof(int), "large enough")
        )
    ) ;
};

While currently I am implementing:

CONTRACT_CLASS( // option B
template( typename T )
class (vector)
) {
    CONTRACT_CLASS_INVARIANT(
        empty() == (size() == 0),
        size() <= capacity
    )
    
public:
    CONTRACT_FUNCTION_TPL(
    public void (push_back) ( (const T&) value )
        precondition(
            size() < max_size()
        )
        postcondition(
            auto old_size = CONTRACT_OLDOF size(),
            auto old_capacity = CONTRACT_OLDOF capacity(),
            back() == val, requires boost::has_equal_to<T>::value,
            size() == old_size + 1,
            capacity() >= old_capacity,
            const( x, y ) x == y,
            static_assert(sizeof(T) >= sizeof(int), "large enough")
        )
    ) ;
};

I think option B (current) is still better than option A because A requires
(1) more parenthesis and (2) the extra assertion word spelled out all the
times but A doesn't require the trailing `,` which is a plus.

Do you have a strong opinion about which one is better between A and B? I'd
say B is better but I'm quite biased at this point ;)

Thanks a lot.
--Lorenzo

--
View this message in context: http://boost.2283326.n4.nabble.com/contract-syntax-redesign-tp3563993p3847911.html
Sent from the Boost - Dev mailing list archive at Nabble.com.