Iterates F(D,X) while C(D,X) is true.
In other words, expands to:
F(D, ... F(D, F(D,X) ) ... )
The depth of iteration is determined by C(D,X).
Legend
- X is the current state of iteration. The state is usually a tuple.
- C is the condition for iteration. It must expand to a decimal
integer literal.
- F is the iterated macro. Note that if the state is a tuple, then
F(D,X) usually expands to a tuple of the same number of elements.
- D is the recursion depth and should only be used as a parameter
to other macros using BOOST_PP_WHILE(). Such macros include
BOOST_PP_ADD() and other arithmetic operations. For each macro using
BOOST_PP_WHILE(), there is a version of the macro, distinguished by the
D suffix (e.g. BOOST_PP_ADD_D()), that accepts an additional recursion
depth as the first parameter. This technique is necessary to avoid
recursively expanding the same macro again, which is not permitted by the
C++ preprocessor. Note that the value of the D parameter may exceed
BOOST_PP_LIMIT_MAG.
Note
Using BOOST_PP_WHILE() is a bit tricky. This is due to the C++ preprocessor
limitations. It is recommended to take a look at the implementations of the
various PREPROCESSOR library primitives such as BOOST_PP_ADD() for
additional examples.
Example
Implementation rationale
- The maximum iteration depth is greater than 2*BOOST_PP_LIMIT_MAG to make
it possible to compute N*N functions.
(C) Copyright Housemarque Oy 2002
Permission to copy, use, modify, sell and distribute this document is granted
provided this copyright notice appears in all copies. This document is provided
"as is" without express or implied warranty, and with no claim as to its suitability
for any purpose.
Generated: