lazy_protect_args

Synopsis

template <class Exp>
struct lazy_protect_args
{
  // unspecified
};

Description

Exp is an angly bracket expression of metafunctions calling each other with other angly bracket expressions as arguments. When lazy_protect_args is used inside lazy, the content of lazy_protect_args is not transformed by lazy, but Exp itself is evaluated before it is passed to the metafunction calling it. When lazy_protect_args is used outside of lazy, it does not change the meaning of the wrapped expression.

Header

#include <mpllibs/metamonad/lazy_protect_args.hpp>

Expression semantics

For any t1, t2 template classes, i >= 0, j >= 0, k >= 0 and a1, ..., ai, b1, ..., bj, c1, ..., ck classes, the following are equivalent

lazy<t1<a1, ..., ai, lazy_protect_args<t2<b1, ..., bj>>, c1, ..., ck>>::type
lazy<t1<a1, ..., ai, t2<already_lazy<b1>, ..., already_lazy<bj>>, c1, ..., ck>
  ::type

lazy_protect_args<t2<b1, ..., bj>>::type
t2<b1, ..., bj>::type

Example

using namespace mpllibs::metamonad::name;

lazy<
  mpl::plus<
    lazy_protect_args<eval_let<x, mpl::int_<13>, mpl::times<x, x>>>,
    mpl::int_<11>
  >
>::type

Copyright Abel Sinkovics (abel at elte dot hu) 2011. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt

[up]