111 lines
2.6 KiB
ReStructuredText
111 lines
2.6 KiB
ReStructuredText
.. Algorithms/Transformation Algorithms//replace_if |50
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replace_if
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==========
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Synopsis
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--------
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.. parsed-literal::
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template<
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typename Sequence
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, typename Pred
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, typename NewType
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, typename In = |unspecified|
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>
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struct replace_if
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{
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typedef |unspecified| type;
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};
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Description
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-----------
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Returns a copy of the original sequence where every type that satisfies
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the predicate ``Pred`` has been replaced with ``NewType``.
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|transformation algorithm disclaimer|
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Header
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------
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.. parsed-literal::
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#include <boost/mpl/replace_if.hpp>
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Model of
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--------
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|Reversible Algorithm|
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Parameters
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----------
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+---------------+-----------------------------------+-------------------------------+
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| Parameter | Requirement | Description |
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+===============+===================================+===============================+
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| ``Sequence`` | |Forward Sequence| | An original sequence. |
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+---------------+-----------------------------------+-------------------------------+
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| ``Pred`` | Unary |Lambda Expression| | A replacement condition. |
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+---------------+-----------------------------------+-------------------------------+
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| ``NewType`` | Any type | A type to replace with. |
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+---------------+-----------------------------------+-------------------------------+
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| ``In`` | |Inserter| | An inserter. |
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+---------------+-----------------------------------+-------------------------------+
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Expression semantics
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--------------------
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|Semantics disclaimer...| |Reversible Algorithm|.
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For any |Forward Sequence| ``s``, an unary |Lambda Expression| ``pred``,
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an |Inserter| ``in``, and arbitrary type ``x``:
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.. parsed-literal::
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typedef replace_if<s,pred,x,in>::type r;
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:Return type:
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A type.
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:Semantics:
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Equivalent to
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.. parsed-literal::
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typedef lambda<pred>::type p;
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typedef transform< s, if_< apply_wrap1<p,_1>,x,_1>, in >::type r;
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Complexity
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----------
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Linear. Performs exactly ``size<s>::value`` applications of ``pred``, and at most
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``size<s>::value`` insertions.
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Example
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-------
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.. parsed-literal::
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typedef vector_c<int,1,4,5,2,7,5,3,5> numbers;
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typedef vector_c<int,1,4,0,2,0,0,3,0> expected;
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typedef replace_if< numbers, greater<_,int_<4> >, int_<0> >::type result;
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BOOST_MPL_ASSERT(( equal< result,expected, equal_to<_,_> > ));
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See also
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--------
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|Transformation Algorithms|, |Reversible Algorithm|, |reverse_replace_if|, |replace|, |remove_if|, |transform|
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