On Wed, Nov 11, 2009 at 9:24 AM, Roman Perepelitsa
2009/11/11 Emanuele Rocci
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
::type _msg_a(constant("my msg")); constant_type<const std::string>::type _msg_b(constant("my msg")); constant_typestd::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
#include int main() { boost::function f = boost::lambda::constant("hello"); std::cout << f() << std::endl; }
Or BOOST_AUTO (which will have lower overhead then Boost.Function).