Re: [boost] [bind/lambda] Matching signature constness?

Subject: Re: [boost] [bind/lambda] Matching signature constness?
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2008-12-10 13:42:23

Robert Jones wrote:
> Here's a bit of code (and my apologies for it's length, but I'm unsure
> which bit is the failure point)
> 

[snip]

>   template < bool >
>     struct cmp_detail
>   {
>     template < typename T >
>       static bool cmp( const T & lhs, const T & rhs )
>     {
>       return lhs != rhs;
>     }
>   };
> 
>   template < >
>     struct cmp_detail< true >
>   {
>     template < typename T, std :: size_t sz >
>       static bool cmp( const T ( & lhs )[ sz ], const T ( & rhs )[ sz ] )
>     {
>       using boost :: lambda :: _1;
>       using boost :: lambda :: bind;
>       using boost :: lambda :: var;
> 
>       boost :: function< bool( unsigned ) > cmp_element =
>         bind( cmp_detail< boost :: is_array< T > :: value > :: cmp,
>             var( lhs )[ _1 ], var( rhs )[ _1 ] );
> 

[snip]

> 
> The problem is the bind call in cmp_detail<true>::cmp(...). Error is this
> 
> block.cpp: In static member function `static bool <unnamed>::cmp_detail<
> true>::cmp(const T (&)[sz], const T (&)[sz]) [w
> ith T = int[16], unsigned int sz = 16u]':
> block.cpp:45:   instantiated from `bool <unnamed>::cmp(const T&, const T&)
> [with T = int[16][16]]'
> block.cpp:61:   instantiated from here
> block.cpp:32: error: no matching function for call to `bind(<unknown type>,

[snip]

I see two problems here:
1. cmp_detail<true>::cmp is a template, but you don't specify its
template parameters in the bind expression.
2. You missed the & operator while taking address of the member function
cmp.

So I guess it should be:

  bind( &cmp_detail< boost :: is_array< T > :: value > :: cmp< T >,
        var( lhs )[ _1 ], var( rhs )[ _1 ] );