catch_just

Synopsis

template <class E, class Pred, class Handler>
struct catch_just
{
  // unspecified
};

Description

Evaluates the angle-bracket expression E. When it evaluates to an exception, the value wrapped by exception is passed to the predicate Pred. If it returns true, the value is passed to the metafunction class Handler and its result is returned by catch_all. When there is no exception or the predicate returns false, catch_just returns the result of E.

Header

#include <mpllibs/metamonad/catch_just.hpp>

Expression semantics

For any t angle-bracket expression not evaluating to an instance of exception, p predicate, u angle-bracket expression evaluating to exception<e> for some e type, pt predicate returning true for e, pf predicate returning false for e and f metafunction class taking one argument the following are equivalent:

catch_all<syntax<t>, p, f>::type
t::type

catch_all<syntax<u>, pt, f>::type
f::type::apply<e>::type

catch_all<syntax<u>, pf, f>::type
u::type

Example

using boost::mpl::int_;
using namespace mpllibs::metamonad::name;

catch_just<
  syntax<may_fail2<may_fail1<int_<13>>>>,
  is_tag<list_tag>,
  lambda_c<e, 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

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