placeholders¶
Header¶
#include <boost/hof/placeholders.hpp>
Description¶
The placeholders provide std::bind
compatible placeholders that
additionally provide basic C++ operators that creates bind expressions.
Each bind expression supports constexpr
function evaluation.
Synopsis¶
namespace placeholders {
placeholder<1> _1 = {};
placeholder<2> _2 = {};
placeholder<3> _3 = {};
placeholder<4> _4 = {};
placeholder<5> _5 = {};
placeholder<6> _6 = {};
placeholder<7> _7 = {};
placeholder<8> _8 = {};
placeholder<9> _9 = {};
}
Operators¶
Binary operators: +,-,*,/,%,>>,<<,>,<,<=,>=,==,!=,&,^,|,&&,||
Assign operators: +=,-=,*=,/=,%=,>>=,<<=,&=,|=,^=
Unary operators: !,~,+,-,*,++,–
Example¶
#include <boost/hof.hpp>
#include <cassert>
using namespace boost::hof;
int main() {
auto sum = _1 + _2;
assert(3 == sum(1, 2));
}
unamed placeholder¶
Header¶
#include <boost/hof/placeholders.hpp>
Description¶
The unamed placeholder can be used to build simple functions from C++ operators.
Note: The function produced by the unamed placeholder is not a bind expression.
Synopsis¶
namespace placeholders {
/* unspecified */ _ = {};
}
Example¶
#include <boost/hof.hpp>
#include <cassert>
using namespace boost::hof;
int main() {
auto sum = _ + _;
assert(3 == sum(1, 2));
}