Re: [Boost-users] [function,bind] Templated function<> function

From: Michiel Helvensteijn (m.helvensteijn_at_[hidden])
Date: 2008-07-16 19:53:23

Steven Watanabe wrote:

>> But you understand why I'd like the templated version to
>> work. I have other predicates to test
> 
> Ok.  The compiler can't deduce T in
> 
> template <class T>
> function<bool (T)> neg(function<bool (T)> func);
> 
> unless the argument is already a boost::function.  No implicit conversions
> allowed.

I suspected it was too much to ask for. But I didn't know any alternative.

> template<class F>
> struct not_t {
>     typedef bool result_type;
>     template<class T>
>     bool operator()(const T& t) { return(!f(t)); }
>     F f;
> };
> 
> template<class F>
> not_t<F> neg(F f) {
>     not_t<F> result = { f };
>     return(result);
> }

This works as expected! So it's a function object, huh. I haven't used those
before. I changed your solution in two small ways:

* I removed the unused typedef.
* I added some overloads of operator() to handle multiple parameters.

This is a useful feature to have. Thanks for your help!

-- 
Michiel Helvensteijn