P99: P99

◆ P99_FOR

#define P99_FOR	(	NAME,
		N,
		OP,
		FUNC,
		...
	)

A preprocessor pseudo iterator.

Parameters

NAME	a name or other data that is visible to all iterations
N	the number of times the iteration is to be done
OP	an operation that is performed to glue the different results of the individual iterations together
FUNC	a function that is applied in each iteration

In each iteration, FUNC will be called as FUNC(NAME, X, I). Here NAME is the same as the argument to P99_FOR. I is the ordinal number of this iteration step, starting from 0. X is the Ith argument from the remaining argument list of this invocation of P99_FOR.

OP is called for iterations 1 to N - 1 to glue the results of the N iterations together. It is called in the form OP(NAME, I, REC, RES), where NAME and I are as before. REC is the result of all iterations with index less than I, RES is the result of the current iteration.

#define P00_SEP(NAME, I, REC, RES) REC; RES
#define P00_VASSIGN(NAME, X, I) X = (NAME)[I]
 
P99_FOR(A, 2, P00_SEP, P00_VASSIGN, toto, tutu);

Will result in

toto = (A)[0]; tutu = (A)[1];

To understand the associativity of the OP argument

#define P00_SUM(NAME, I, REC, RES) ((REC) + (RES))
#define P00_IDT(NAME, X, I) X
 
P99_FOR(A, 2, P00_SUM, P00_IDT, a, b, c)

Will result in

((((a) + (b))) + (c))

Warning: argument 0 may be evaluated multiple times

Remarks: argument 1 must expand to a decimal number; argument 3 should correspond to a macro name

Definition at line 92 of file p99_for.h.