Greetings,
I'm a newbie, at least to Boost, and I have been playing around with it to get
familiar with it, and to improve my c++ skills. :)
I've run into two problems with boost::bind (and I suspect there is a connection
with boost::function). The two programs at the bottom of this message
demonstrate these problems.
Can anybody shed a light on this? Are these errors in Boost, or did I miss
something in the documentation? Should I ask on another mailing list? Or should
I file a bug report?
Platform: linux-x86
Compiler: GNU C++ version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)
STL : GNU libstdc++ version 20061115
Boost : 1.35.0
Regards,
Jeroen.
------------------------------------------------------------------------
#include
#include
bool doit(int i)
{
return i > 0;
}
int main(void)
{
boost::function1 mything;
mything = boost::bind(doit, 3);
// The statement below results in error:
// bind-and-function.cpp:24: error: no match for call to
// $-1òø(boost::function1boost::function_base >) ()$-1òù
// /usr/include/boost/function/function_template.hpp:819: note:
// candidates are: typename boost::function1::result_type boost::function1::operator()(T0) const [with R = bool, T0 = int,
// Allocator = std::allocatorboost::function_base]
return mything() ? 0 : 1;
}
------------------------------------------------------------------------
#include
#include
#include <cassert>
struct anything
{
void operator()(int var1, int var2,
boost::function1& mything)
{
assert(var1 == 12345);
assert(var2 == 67890);
mything(var1 + var2);
}
void one_arg(int var3, int var4)
{
assert(var3 == var4);
}
} something;
int main(void)
{
// Building and running an expression in small steps works.
boost::function1 one_arg_f =
boost::bind(&anything::one_arg, &something, _1, 80235);
boost::function2 parentheses_f =
boost::bind(&anything::operator(), &something, _1, _2,
one_arg_f);
parentheses_f(12345, 67890);
// This also works.
boost::bind(&anything::operator(), &something, _1, _2,
one_arg_f)(12345, 67890);
// Change either zero in the preprocessor consitionals to one to
// demonstrate the problem. In my setup, changing both zeroes to
// ones results only in an error message for the first statement.
// Leaving both zeroes in place makes this code compile and run to an
// exit code of zero.
#if 0
// But replacing one_arg_f by its value fails to compile:
// /usr/include/boost/bind.hpp:413: error: invalid use of void
// expression
boost::bind(&anything::operator(), &something, _1, _2,
boost::bind(&anything::one_arg, &something, _1, 80235))
(12345, 67890);
#elif 0
// Separating construction and execution does not help, but shows it
// is the construction that is failing.
boost::function2 parentheses_f2 =
boost::bind(&anything::operator(), &something, _1, _2,
boost::bind(&anything::one_arg, &something, _1, 80235));
parentheses_f2(12345, 67890);
#endif
// Replacing the second _1 by _3 results in even weirder error messages.
return 0;
}
------------------------------------------------------------------------
