Re: [boost] [contract] C++11-like auto-functions

Subject: Re: [boost] [contract] C++11-like auto-functions
From: lcaminiti (lorcaminiti_at_[hidden])
Date: 2012-07-02 09:19:15

Dave Abrahams wrote
> 
> on Wed Jun 27 2012, Lorenzo Caminiti <lorcaminiti-AT-gmail.com> wrote:
> 
>> Hello all,
>>
>> I'm thinking to expand Boost.Contract to support C++11-like
>> auto-functions for C++03.
>>
>> I got a ticket for it:
>> https://sourceforge.net/apps/trac/contractpp/ticket/59
>> But I might implement it only after the Boost review... (Are C++11
>> auto-function really useful?)
> 
> auto functions arelly are useful, but mostly they're useful with a macro
> that calculates noexcept, return type, etc.:
> http://lists.boost.org/Archives/boost/2012/04/191926.php
> 

I see but that only applies to C++11 and not to auto-functions emulated in
C++03 (because there's no noexcept in C++03). Also, these type of macros
only apply to 1-liner functions (of course, as you show using operator, you
can concatenate a bunch of expressions on a single line).

Contract++ could support something like that:

// auto swap(B& x, B& y) RETURNS(swap(x.a,y.a), swap(x.b,y.b), ...);

struct B { A a, b; }

// Defines swap to return `return ...` and automatically figures out
noexcept (on C++11).
CONTRACT_FUNCTION_DEF(
    auto (swap) ( (B&) x, (B&) y )
        return(swap(x.a, y.a), swap(x.b, y.b))
)

I'll think more about this when/if I implement auto-functions support for
Contract++.

--Lorenzo

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