Re: [boost] [contract] Macro syntax?

Subject: Re: [boost] [contract] Macro syntax?
From: Jeffrey Hellrung (jhellrung_at_[hidden])
Date: 2010-03-27 22:42:11

Lorenzo Caminiti wrote:
> Hello,
> 
> I would like to renew the request for all of you to express an opinion
> between OPTION 1 and 2 below. I am NOT asking you to understand
> Boost.Contract. On the contrary, the less you know about
> Boost.Contract the more your input is valuable for me.
> 
> Please just indicate which syntax between OPTION 1 and 2 you would
> like the most (or dislike the least ;) ) to see in your header files.
> 
> On Sat, Mar 20, 2010 at 10:54 AM, Lorenzo Caminiti
> <lorcaminiti_at_[hidden]> wrote:
>> OPTION 1: The function declaration is programmed using the usual C++
>> syntax just before the CONTRACT_FUNCTION() macro.
>>
>>    template<typename T>
>>    class myvector {
>>
>>        CONTRACT_INVARIANT( ({
>>            ...
>>        }) )
>>
>>    public:
>>        void push_back(const T& element) // Usual C++ push_back() declaration.
>>        CONTRACT_FUNCTION( (class) (copyable)(myvector)
>>                (public) (void) (push_back)( (const T&)(element) )
>>        (precondition)({
>>            ...
>>        })
>>        (postcondition)({
>>            ...
>>        })
>>        (body)({
>>            ...
>>        }) )
>>
>>        ...
>>    };
>>
>> OPTION 2: The CONTRACT_FUNCTION() macro automatically programs also
>> the function declaration.
>>
>>    template<typename T>
>>    class myvector {
>>
>>        CONTRACT_INVARIANT( ({
>>            ...
>>        }) )
>>
>>    public:
>>        // No usual C++ push_back() declaration here.
>>        CONTRACT_FUNCTION( (class) (copyable)(myvector)
>>                (public) (void) (push_back)( (const T&)(element) )
>>        (precondition)({
>>            ...
>>        })
>>        (postcondition)({
>>            ...
>>        })
>>        (body)({
>>            ...
>>        }) )
>>
>>        ...
>>    };
> 
> Thanks a lot!
> Lorenzo

Well, knowing very little about Boost.Contract except what I glean from 
the mailing list messages, I'd prefer OPTION 2, but with some minor 
tweaks.  E.g., can the public/private/protected specification just be 
whatever the access is as the point of the macro invocation?  I'd also 
prefer "(( const T&, element ))" to "( const T& ) ( element )", and 
perhaps a usage recommendation would be to #define the "( class ) ( 
copyable ) ( myvector )" to some preprocessor symbol so that you don't 
have to type it out for every CONTRACT_FUNCTION invocation.  Perhaps you 
can have a variant of CONTRACT_FUNCTION that just uses some predefined 
macro to get the information encapsulated in "( class ) ( copyable ) ( 
myvector )" ?  This might alleviate the parentheses problem, e.g.,

OTHER_CONTRACT_FUNCTION( public, void, push_back, (( const T&, element )) )

Also, are there going to be more design decision queries sent to the 
mailing list where "less knowledge is better"?  If so, I will do my 
damnedest to remain ignorant ;)

- Jeff