Re: [Boost-users] naming delayed variables string in boost lamdba

Subject: Re: [Boost-users] naming delayed variables string in boost lamdba
From: Roman Perepelitsa (roman.perepelitsa_at_[hidden])
Date: 2009-11-11 11:24:35

2009/11/11 Emanuele Rocci <rocciemanuele_at_[hidden]>

>  Hi All
> I am getting familiar with boost::lambda.
> Today I learnt about delayed variable and usage of boost::constant in
> lambda expression.
> Do you know why when I try to declare delayed variables for string like I
> do below
> the compiler gives me each time an error?
> I tried the following
>
> constant_type<const char*>::type _msg_a(constant("my msg"));
> constant_type<const std::string>::type _msg_b(constant("my msg"));
> constant_type<std::string>::type _msg_c(constant("my msg"));
>
> If I use constant( "my msg" ) inside a boost lambda expression everything
> is fine but I cannot declare correctly a delayed variable.
> Do you know how to fix it or where I can get some details?
> Thanks in advance
> Mn
>

Function objects generated by lambda have unspecified types. If you want to
save them, use Boost.Function.

#include <iostream>
#include <boost/lambda/core.hpp>
#include <boost/function.hpp>

int main() {
  boost::function<const char*()> f = boost::lambda::constant("hello");
  std::cout << f() << std::endl;
}

Roman Perepelitsa