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< title > BOOST_PP_FOR< / title >
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The < b > BOOST_PP_FOR< / b > macro represents a generalized horizontal repetition construct.
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< h4 > Usage< / h4 >
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< b > BOOST_PP_FOR< / b > (< i > state< / i > , < i > pred< / i > , < i > op< / i > , < i > macro< / i > )
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< h4 > Arguments< / h4 >
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< dt > state< / dt >
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The initial state.
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< dt > pred< / dt >
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A binary predicate of the form < i > pred< / i > (< i > r< / i > , < i > state< / i > ).
This macro must expand to an integer in the range of < i > 0< / i > to < b > BOOST_PP_LIMIT_MAG< / b > .
< b > BOOST_PP_FOR< / b > repeatedly expands < i > macro< / i > while this predicate returns non-zero.
This macro is called with the next available < b > BOOST_PP_FOR< / b > repetition and the current < i > state< / i > .
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< dt > op< / dt >
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A binary operation of the form < i > op< / i > (< i > r< / i > , < i > state< / i > ).
This operation is expanded by < b > BOOST_PP_FOR< / b > with the next available < b > BOOST_PP_FOR< / b > repetition and the current < i > state< / i > .
This macro is repeatedly applied to the < i > state< / i > , each time producing a new < i > state< / i > , until < i > pred< / i > returns < i > 0< / i > .
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< dt > macro< / dt >
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A binary macro of the form < i > macro< / i > (< i > r< / i > , < i > state< / i > ).
This macro is expanded by < b > BOOST_PP_FOR< / b > with the next available < b > BOOST_PP_FOR< / b > repetition and the current < i > state< / i > .
This macro is is repeated by < b > BOOST_PP_FOR< / b > until < i > pred< / i > returns < i > 0< / i > .
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< h4 > Remarks< / h4 >
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This macro expands to the sequence:
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< i > macro< / i > (< i > r< / i > , < i > state< / i > ) < i > macro< / i > (< i > r< / i > , < i > op< / i > (< i > r< / i > , < i > state< / i > )) ... < i > macro< / i > (< i > r< / i > , < i > op< / i > (< i > r< / i > , ... < i > op< / i > (< i > r< / i > , < i > state< / i > ) ... ))
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The < i > r< / i > value that is passed to < i > pred< / i > , < i > op< / i > , and < i > macro< / i > represents the next available < b > BOOST_PP_FOR< / b > repetition.
Other macros that have < b > _R< / b > suffix variants internally use < b > BOOST_PP_FOR< / b > --for example, < b > BOOST_PP_LIST_FOR_EACH< / b > and < b > BOOST_PP_LIST_FOR_EACH_R< / b > .
Using these < b > _R< / b > versions is not strictly necessary, but passing the < i > r< / i > value (that is passed to < i > pred< / i > , < i > op< / i > , and < i > macro< / i > ) to these macros allows them to reenter < b > BOOST_PP_FOR< / b > with maximum efficiency.
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To directly use this < i > r< / i > value, rather than simply passing it to another macro, see < b > BOOST_PP_FOR_< i > r< / i > < / b > .
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Previously, this macro could not be used recursively inside < b > BOOST_PP_FOR< / b > .
This limitation no longer exists, as the library can automatically detect the next available < b > BOOST_PP_FOR< / b > repetition.
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< h4 > See Also< / h4 >
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< li > < a href = "for_r.html" > BOOST_PP_FOR_< i > r< / i > < / a > < / li >
< li > < a href = "limit_mag.html" > BOOST_PP_LIMIT_MAG< / a > < / li >
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< h4 > Requirements< / h4 >
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< b > Header:< / b > < a href = "../headers/repetition/for.html" > < boost/preprocessor/repetition/for.hpp> < / a >
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< h4 > Sample Code< / h4 >
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#include < < a href = "../headers/arithmetic/inc.html" > boost/preprocessor/arithmetic/inc.hpp< / a > >
#include < < a href = "../headers/comparison/not_equal.html" > boost/preprocessor/comparison/not_equal.hpp< / a > >
#include < < a href = "../headers/repetition/for.html" > boost/preprocessor/repetition/for.hpp< / a > >
#include < < a href = "../headers/tuple/elem.html" > boost/preprocessor/tuple/elem.hpp< / a > >
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#define PRED(r, state) \
< a href = "not_equal.html" > BOOST_PP_NOT_EQUAL< / a > ( \
< a href = "tuple_elem.html" > BOOST_PP_TUPLE_ELEM< / a > (2, 0, state), \
< a href = "inc.html" > BOOST_PP_INC< / a > (< a href = "tuple_elem.html" > BOOST_PP_TUPLE_ELEM< / a > (2, 1, state)) \
) \
/**/
#define OP(r, state) \
( \
< a href = "inc.html" > BOOST_PP_INC< / a > (< a href = "tuple_elem.html" > BOOST_PP_TUPLE_ELEM< / a > (2, 0, state)), \
< a href = "tuple_elem.html" > BOOST_PP_TUPLE_ELEM< / a > (2, 1, state) \
) \
/**/
#define MACRO(r, state) < a href = "tuple_elem.html" > BOOST_PP_TUPLE_ELEM< / a > (2, 0, state)
< a href = "for.html" > BOOST_PP_FOR< / a > ((5, 10), PRED, OP, MACRO) // expands to 5 6 7 8 9 10
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