From: David Brownell (brownell_at_[hidden])
Date: 2001-10-15 17:33:57
Thanks for your help, that got me over my hurdle!
-----Original Message-----
From: Wilka [mailto:wilka_at_[hidden]]
Sent: Monday, October 15, 2001 1:57 PM
To: boost_at_[hidden]
Subject: RE: [boost] Function and Bind
When you're passing a functor (such as boost::function) to a
boost::function, you need to explicitly tell it what the return value is. So
in your case, if you change:
<code>
//BEGIN PROBLEM
OneArgFunction f_oneArg;
f_oneArg = boost::bind(f2, ulValue, _1);
//END PROBLEM
return(DoIt_One(f_oneArg));
</code>
To
<code>
//BEGIN PROBLEM
OneArgFunction f_oneArg;
f_oneArg = boost::bind<bool>(f2, ulValue, _1); // Note the "<bool>" //END
PROBLEM return(DoIt_One(f_oneArg)); </code>
It should work fine.
- Wilka
> -----Original Message-----
> From: brownell_at_[hidden] [mailto:brownell_at_[hidden]]
> Sent: 15 October 2001 21:15
> To: boost_at_[hidden]
> Subject: [boost] Function and Bind
>
>
> I have a question that is probably better asked in code than in
> words, but I will try the words route first, and if that doesn't
> work, I have pasted code that may explain the situation better.
>
> I have one function that takes 1 arg (call it Func1), another that
> takes 2 args (call it Func2). Both these functions take
> boost::functionX params. Somehow, I need to bind a value to the
> first arg in Func2, and pass that new function to Func1.
>
> I can not wait for the return value of Func1, as these function are
> used to update algorithm progress.
>
> Make any sense? Hopefully the code will.
>
> Thanks for any and all help,
> Dave Brownell
>
> #include<iostream>
>
> #include "boost\bind.hpp"
> #include "boost\Function.hpp"
>
> typedef boost::function1<bool, unsigned long>
> OneArgFunction;
> typedef boost::function2<bool, unsigned long, unsigned long>
> TwoArgFunction;
>
> inline bool WriteOne(unsigned long ul1)
> {
> std::cout << ul1 << std::endl;
> return(true);
> }
>
> inline bool WriteTwo(unsigned long ul1, unsigned long ul2)
> {
> std::cout << "(" << ul2 << ") " << ul1 << std::endl;
> return(true);
> }
>
> bool DoIt_One(OneArgFunction &f)
> {
> if(f.empty() == false)
> f(1);
>
> return(true);
> }
>
> bool DoIt_Two(TwoArgFunction &f2, unsigned long ulValue)
> {
> if(f.empty() == false)
> return(false);
>
> //BEGIN PROBLEM
> OneArgFunction f_oneArg;
>
> f_oneArg = boost::bind(f2, ulValue, _1);
> //END PROBLEM
> return(DoIt_One(f_oneArg));
> }
>
> int main(void)
> {
> TwoArgFunction f2 = &WriteTwo;
>
> DoIt_Two(f2, 2);
>
> return(true);
> }
>
>
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