293 lines
17 KiB
C++
293 lines
17 KiB
C++
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// (C) Copyright Edward Diener 2011-2015
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// Use, modification and distribution are subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt).
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#if !defined(BOOST_VMD_ELEM_HPP)
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#define BOOST_VMD_ELEM_HPP
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#include <boost/vmd/detail/setup.hpp>
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#if BOOST_PP_VARIADICS
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#include <boost/vmd/detail/modifiers.hpp>
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#include <boost/vmd/detail/sequence_elem.hpp>
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/*
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The succeeding comments in this file are in doxygen format.
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*/
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/** \file
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*/
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/** \def BOOST_VMD_ELEM(elem,...)
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\brief Accesses an element of a sequence.
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elem = A sequence element number. From 0 to sequence size - 1.
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... = Variadic parameters.
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The first variadic parameter is required and is the sequence to access.
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Further variadic parameters are all optional.
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With no further variadic parameters the macro returns the particular element
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in the sequence. If the element number is outside the bounds of the sequence
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macro access fails and the macro turns emptiness.
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Optional parameters determine what it means that an element is successfully
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accessed as well as what data is returned by the macro.
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Filters: specifying a VMD type tells the macro to return the element only
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if it is of the VMD type specified, else macro access fails. If more than
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one VMD type is specified as an optional parameter the last one
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specified is the filter.
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Matching Identifiers: If the filter is specified as the identifier type, BOOST_VMD_TYPE_IDENTIFIER,
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optional parameters which are identifiers specify that the element accessed
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must match one of the identifiers else access fails. The identifiers may be specified multiple
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times as single optional parameters or once as a tuple of identifier
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parameters. If the identifiers are specified as single optional parameters
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they cannot be any of the specific BOOST_VMD_ optional parameters in order to be
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recognized as matching identifiers. Normally this should never be the case.
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The only situation where this could occur is if the VMD types, which are filters,
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are used as matching identifiers; in this case the matching identifiers need
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to be passed as a tuple of identifier parameters so they are not treated
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as filters.
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Filters and matching identifiers change what it means that an element is successfully
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accessed. They do not change what data is returned by the macro. The remaining optional
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parameters do not change what it means that an element is successfully accessed but they
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do change what data is returned by the macro.
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Splitting: Splitting allows the macro to return the rest of the sequence
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after the element accessed.
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If BOOST_VMD_RETURN_AFTER is specified the return is a tuple
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with the element accessed as the first tuple parameter and the rest of
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the sequence as the second tuple parameter. If element access fails
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both tuple parameters are empty.
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If BOOST_VMD_RETURN_ONLY_AFTER
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is specified the return is the rest of the sequence after the element accessed
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found. If the element access fails the return is emptiness.
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If BOOST_VMD_RETURN_NO_AFTER, the default, is specified no splitting
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occurs.
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If more than one of the splitting identifiers are specified
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the last one specified determines the splitting.
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Return Type: The element accessed can be changed to return both the type
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of the element as well as the element data with optional return type
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parameters. When a type is returned, the element accessed which is returned becomes a
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two-element tuple where the type of the element accessed is the first tuple element and the element
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data itself is the second tuple element. If the macro fails to access the
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element the element access returned is emptiness and not a tuple.
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If BOOST_VMD_RETURN_NO_TYPE, the default, is specified no type is returned
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as part of the element accessed.
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If BOOST_VMD_RETURN_TYPE is specified the specific type of the element
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is returned in the tuple.
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If BOOST_VMD_RETURN_TYPE_ARRAY is specified
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an array type is returned if the element is an array, else a tuple
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type is returned if the element is a tuple, else the actual type
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is returned for non-tuple data.
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If BOOST_VMD_RETURN_TYPE_LIST is specified
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a list type is returned if the element is a list, else a tuple
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type is returned if the element is a tuple, else the actual type
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is returned for non-tuple data.
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If BOOST_VMD_RETURN_TYPE_TUPLE is specified
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a tuple type is returned for all tuple-like data, else the actual type
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is returned for non-tuple data.
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If more than one return type optional
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parameter is specified the last one specified determines the return type.
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If a filter is specified optional return type parameters are ignored and
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the default BOOST_VMD_RETURN_NO_TYPE is in effect.
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Index: If the filter is specified as the identifier type, BOOST_VMD_TYPE_IDENTIFIER,
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and matching identifiers are specified, an index parameter specifies that the
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numeric index, starting with 0, of the matching identifier found, be returned
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as part of the result.
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If BOOST_VMD_RETURN_INDEX is specified an index is returned
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as part of the result.
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If BOOST_VMD_RETURN_NO_INDEX, the default, is specified
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no index is returned as part of the result.
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If both are specified the last one specified determines the index parameter.
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When an index is returned as part of the result, the result is a tuple where the
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element accessed is the first tuple parameter and the index is the last tuple parameter.
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If element access fails the index is empty. If there is no BOOST_VMD_TYPE_IDENTIFIER
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filter or if there are no matching identifiers the BOOST_VMD_RETURN_INDEX is ignored
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and no index is returned as part of the result.
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returns = With no optional parameters the element accessed is returned, or emptiness if
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element is outside the bounds of the sequence. Filters and matching identifiers
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can change the meaning of whether the element accessed is returned or failure
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occurs, but whenever failure occurs emptiness is returned as the element access part
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of that failure, else the element accessed is returned. Return type optional parameters,
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when filters are not used, return the element accessed as a two-element tuple
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where the first tuple element is the type and the second tuple element is the
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data; if the element is not accessed then emptiness is returned as the element access
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and not a tuple. Splitting with BOOST_VMD_RETURN_AFTER returns a tuple where the element accessed
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is the first tuple element and the rest of the sequence is the second tuple element.
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Splitting with BOOST_VMD_RETURN_ONLY_AFTER returns the rest of the sequence after
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the element accessed or emptiness if the element can not be accessed. Indexing
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returns the index as part of the output only if filtering with
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BOOST_VMD_TYPE_IDENTIFIER is specified and matching identifiers are specified.
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When the index is returned with BOOST_VMD_RETURN_AFTER it is the third element
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of the tuple returned, else it is the second element of a tuple where the element
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accessed is the first element of the tuple.
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*/
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#define BOOST_VMD_ELEM(elem,...) \
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BOOST_VMD_DETAIL_SEQUENCE_ELEM(BOOST_VMD_ALLOW_ALL,elem,__VA_ARGS__) \
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/**/
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/** \def BOOST_VMD_ELEM_D(d,elem,...)
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\brief Accesses an element of a sequence. Re-entrant version.
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d = The next available BOOST_PP_WHILE iteration.
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elem = A sequence element number. From 0 to sequence size - 1.
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... = Variadic parameters.
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The first variadic parameter is required and is the sequence to access.
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Further variadic parameters are all optional.
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With no further variadic parameters the macro returns the particular element
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in the sequence. If the element number is outside the bounds of the sequence
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macro access fails and the macro turns emptiness.
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Optional parameters determine what it means that an element is successfully
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accessed as well as what data is returned by the macro.
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Filters: specifying a VMD type tells the macro to return the element only
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if it is of the VMD type specified, else macro access fails. If more than
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one VMD type is specified as an optional parameter the last one
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specified is the filter.
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Matching Identifiers: If the filter is specified as the identifier type, BOOST_VMD_TYPE_IDENTIFIER,
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optional parameters which are identifiers specify that the element accessed
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must match one of the identifiers else access fails. The identifiers may be specified multiple
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times as single optional parameters or once as a tuple of identifier
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parameters. If the identifiers are specified as single optional parameters
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they cannot be any of the specific BOOST_VMD_ optional parameters in order to be
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recognized as matching identifiers. Normally this should never be the case.
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The only situation where this could occur is if the VMD types, which are filters,
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are used as matching identifiers; in this case the matching identifiers need
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to be passed as a tuple of identifier parameters so they are not treated
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as filters.
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Filters and matching identifiers change what it means that an element is successfully
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accessed. They do not change what data is returned by the macro. The remaining optional
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parameters do not change what it means that an element is successfully accessed but they
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do change what data is returned by the macro.
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Splitting: Splitting allows the macro to return the rest of the sequence
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after the element accessed.
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If BOOST_VMD_RETURN_AFTER is specified the return is a tuple
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with the element accessed as the first tuple parameter and the rest of
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the sequence as the second tuple parameter. If element access fails
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both tuple parameters are empty.
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If BOOST_VMD_RETURN_ONLY_AFTER
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is specified the return is the rest of the sequence after the element accessed
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found. If the element access fails the return is emptiness.
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If BOOST_VMD_RETURN_NO_AFTER, the default, is specified no splitting
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occurs.
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If more than one of the splitting identifiers are specified
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the last one specified determines the splitting.
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Return Type: The element accessed can be changed to return both the type
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of the element as well as the element data with optional return type
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parameters. When a type is returned, the element accessed which is returned becomes a
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two-element tuple where the type of the element accessed is the first tuple element and the element
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data itself is the second tuple element. If the macro fails to access the
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element the element access returned is emptiness and not a tuple.
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If BOOST_VMD_RETURN_NO_TYPE, the default, is specified no type is returned
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as part of the element accessed.
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If BOOST_VMD_RETURN_TYPE is specified the specific type of the element
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is returned in the tuple.
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If BOOST_VMD_RETURN_TYPE_ARRAY is specified
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an array type is returned if the element is an array, else a tuple
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type is returned if the element is a tuple, else the actual type
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is returned for non-tuple data.
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If BOOST_VMD_RETURN_TYPE_LIST is specified
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a list type is returned if the element is a list, else a tuple
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type is returned if the element is a tuple, else the actual type
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is returned for non-tuple data.
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If BOOST_VMD_RETURN_TYPE_TUPLE is specified
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a tuple type is returned for all tuple-like data, else the actual type
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is returned for non-tuple data. If more than one return type optional
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parameter is specified the last one specified determines the return type.
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If a filter is specified optional return type parameters are ignored and
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the default BOOST_VMD_RETURN_NO_TYPE is in effect.
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Index: If the filter is specified as the identifier type, BOOST_VMD_TYPE_IDENTIFIER,
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and matching identifiers are specified, an index parameter specifies that the
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numeric index, starting with 0, of the matching identifier found, be returned
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as part of the result.
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If BOOST_VMD_RETURN_INDEX is specified an index is returned
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as part of the result.
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If BOOST_VMD_RETURN_NO_INDEX, the default, is specified
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no index is returned as part of the result.
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If both are specified the last one specified determines the index parameter.
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When an index is returned as part of the result, the result is a tuple where the
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element accessed is the first tuple parameter and the index is the last tuple parameter.
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If element access fails the index is empty. If there is no BOOST_VMD_TYPE_IDENTIFIER
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filter or if there are no matching identifiers the BOOST_VMD_RETURN_INDEX is ignored
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and no index is returned as part of the result.
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returns = With no optional parameters the element accessed is returned, or emptiness if
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element is outside the bounds of the sequence. Filters and matching identifiers
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can change the meaning of whether the element accessed is returned or failure
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occurs, but whenever failure occurs emptiness is returned as the element access part
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of that failure, else the element accessed is returned. Return type optional parameters,
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when filters are not used, return the element accessed as a two-element tuple
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where the first tuple element is the type and the second tuple element is the
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data; if the element is not accessed then emptiness is returned as the element access
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and not a tuple. Splitting with BOOST_VMD_RETURN_AFTER returns a tuple where the element accessed
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is the first tuple element and the rest of the sequence is the second tuple element.
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Splitting with BOOST_VMD_RETURN_ONLY_AFTER returns the rest of the sequence after
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the element accessed or emptiness if the element can not be accessed. Indexing
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returns the index as part of the output only if filtering with
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BOOST_VMD_TYPE_IDENTIFIER is specified and matching identifiers are specified.
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When the index is returned with BOOST_VMD_RETURN_AFTER it is the third element
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of the tuple returned, else it is the second element of a tuple where the element
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accessed is the first element of the tuple.
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*/
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#define BOOST_VMD_ELEM_D(d,elem,...) \
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BOOST_VMD_DETAIL_SEQUENCE_ELEM_D(d,BOOST_VMD_ALLOW_ALL,elem,__VA_ARGS__) \
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/**/
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#endif /* BOOST_PP_VARIADICS */
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#endif /* BOOST_VMD_ELEM_HPP */
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