On 02/14/2012 10:43 PM, Matt wrote:
Hi there!
I've got a question (two, in fact) regarding Arguments in Boost Phoenix.
Assuming using boost::phoenix::arg_names::arg1; using boost::phoenix::val; using boost::phoenix::ref; using boost::phoenix::cref;
Why does this compile (and works): int x = 1; int y = 2; std::cout << (arg1 % 2 == 1)(x) << '\n'; std::cout << (arg1 % 2 == 1)(y) << '\n';
while these fail to compile (with an extremely long diagnostic involving "boost::error_cant_deduce_type"):
std::cout << (arg1 % 2 == 1)(1) << '\n'; std::cout << (arg1 % 2 == 1)(2) << '\n';
std::cout << (arg1 % 2 == 1)(val(1)) << '\n'; std::cout << (arg1 % 2 == 1)(val(2)) << '\n';
std::cout << (arg1 % 2 == 1)(cref(1)) << '\n'; std::cout << (arg1 % 2 == 1)(cref(2)) << '\n';
I run into this was while attempting to store an Arg. into a variable, i.e.,: auto f = (arg1 % 2 == 1); this works: std::cout << f(x) << '\n'; std::cout << f(y) << '\n'; while this fails: std::cout << f(1) << '\n'; std::cout << f(2) << '\n'; I'm guessing this must be for the same reason the above attempts fail.
You're using Phoenix v2, which doesn't support rvalues and also has many type deduction problems. Try v3.