File size: 1,645 Bytes
8ae5fc5 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 | #ifndef METAL_LAMBDA_ARG_HPP
#define METAL_LAMBDA_ARG_HPP
#include "../config.hpp"
#include <cstddef>
namespace metal {
/// \cond
namespace detail {
template <std::size_t n>
struct _arg;
}
/// \endcond
/// \ingroup lambda
///
/// ### Description
/// A parametric \lambda that selects the n-th argument it is invoked with.
///
/// ### Usage
/// For any nonzero positive integral value `n`
/// \code
/// using result = metal::arg<n>;
/// \endcode
///
/// \returns: \lambda
/// \semantics:
/// Equivalent to
/// \code
/// using result = metal::lambda<expr>;
/// \endcode
/// where `expr` is an \expression such that
/// `expr<val_0, ..., val_n-1, ..., val_m-1>` yields `val_n-1`.
///
/// ### Example
/// \snippet lambda.cpp arg
///
/// ### See Also
/// \see lambda, invoke, bind, always
template <std::size_t n>
using arg = typename detail::_arg<n>::type;
}
#include "../lambda/lambda.hpp"
#include "../list/at.hpp"
#include "../list/list.hpp"
#include "../number/number.hpp"
namespace metal {
/// \cond
namespace detail {
template <std::size_t n>
struct _arg {
template <class... vals>
using impl = at<list<vals...>, number<n - 1>>;
using type = lambda<impl>;
};
template <>
struct _arg<0U> {
};
}
/// \endcond
/// \ingroup lambda
///
/// ### Description
/// Predefined placeholder.
/// \{
using _1 = metal::arg<1U>;
using _2 = metal::arg<2U>;
using _3 = metal::arg<3U>;
using _4 = metal::arg<4U>;
using _5 = metal::arg<5U>;
using _6 = metal::arg<6U>;
using _7 = metal::arg<7U>;
using _8 = metal::arg<8U>;
using _9 = metal::arg<9U>;
/// \}
}
#endif
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