Re: [boost] new utility: function parameter caster

From: Steven Watanabe (steven_at_[hidden])
Date: 2006-12-09 22:06:30

AMDG

"Peter Dimov" wrote:

> ali f wrote:
>   
>> > Hi again,
>> >
>> > ok, here's my actual real world situation:
>> >
>> > win->on_mouse_move.connect(
>> >     args_cast<2, bool(int,int,bool,int)>( (
>> >         lambda::var(x) = lambda::_1,
>> >         lambda::var(y) = lambda::_2,
>> >         true
>> >     ) )
>> >     );
>>     
> The following: win->on_mouse_move.connect( ( lambda::var(x) = 
> lambda::_1, lambda::var(y) = lambda::_2, lambda::_4, true ) ); would 
> be Lambda's way to make it accept four arguments and only use the 
> first two; it doesn't subscribe to boost::bind's philosophy of 
> automatically ignoring extra arguments. Unfortunately, Lambda doesn't 
> have _4, which makes the suggested workaround a bit limited. :-) Your 
> attempt at using boost::bind with it didn't work probably because you 
> didn't specify a return type. Try boost::bind<bool>. 

Even that isn't enough. You need:
    win->on_mouse_move.connect(
    boost::bind<bool>( unlambda((
        lambda::var(x) = lambda::_1,
        lambda::var(y) = lambda::_2,
        true
    )), _1, _2 )
    );
This compiles fine.

In Christ,
Steven Watanabe