| .. Macros/Asserts//BOOST_MPL_ASSERT_RELATION |
| |
| BOOST_MPL_ASSERT_RELATION |
| ========================= |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| #define BOOST_MPL_ASSERT_RELATION( x, relation, y ) \\ |
| |unspecified-token-seq| \\ |
| /\*\*/ |
| |
| |
| |
| Description |
| ----------- |
| |
| A specialized assertion macro for checking numerical conditions. Generates |
| a compilation error when the condition ``( x relation y )`` |
| doesn't hold. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/assert.hpp> |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-----------------------------------+-----------------------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===================================+===============================================+ |
| | ``x`` | An integral constant | Left operand of the checked relation. | |
| +---------------+-----------------------------------+-----------------------------------------------+ |
| | ``y`` | An integral constant | Right operand of the checked relation. | |
| +---------------+-----------------------------------+-----------------------------------------------+ |
| | ``relation`` | A C++ operator token | An operator token for the relation being | |
| | | | checked. | |
| +---------------+-----------------------------------+-----------------------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any integral constants ``x``, ``y`` and a legal C++ operator token ``op``: |
| |
| |
| .. parsed-literal:: |
| |
| BOOST_MPL_ASSERT_RELATION( x, op, y ); |
| |
| :Return type: |
| None. |
| |
| :Semantics: |
| Generates a compilation error if ``( x op y ) != true``, otherwise |
| has no effect. |
| |
| When possible within the compiler's diagnostic capabilities, |
| the error message will include a name of the relation being checked, |
| the actual values of both operands, and have a general form of: |
| |
| .. parsed-literal:: |
| |
| |...| \*\*\*\*\*\*\*\*\*\*\*\*\ |...|\ assert_relation<op, x, y>::\*\*\*\*\*\*\*\*\*\*\*\*) |...| |
| |
| |
| Example |
| ------- |
| |
| :: |
| |
| template< typename T, typename U > struct my |
| { |
| // ... |
| BOOST_MPL_ASSERT_RELATION( sizeof(T), <, sizeof(U) ); |
| }; |
| |
| my<char[50],char[10]> test; |
| |
| // In instantiation of `my<char[50], char[10]>': |
| // instantiated from here |
| // conversion from ` |
| // mpl_::failed************mpl_::assert_relation<less, 50, 10>::************' |
| // to non-scalar type `mpl_::assert<false>' requested |
| |
| |
| See also |
| -------- |
| |
| |Asserts|, |BOOST_MPL_ASSERT|, |BOOST_MPL_ASSERT_NOT|, |BOOST_MPL_ASSERT_MSG| |
| |
| |
| .. copyright:: Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams |
| 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) |
