eladn / applyxn-c-macro

APPLYXn is a macro extension tool for the C preprocessor. It basically receives a macro name and a variable number of items; then applies the macro on each item one-by-one.

APPLYXn is a macro extension tool for the C preprocessor. APPLYXn(..) is a macro itself. When applied, it expects to receive (i) a name of another macro MACRO_NAME, and (ii) a variable number of items item_1, ..., item_n. Such a call would be expanded (by the C preprocessor) into a sequence of n applications of the given MACRO_NAME(..). In the i-th expanded application of MACRO_NAME(..), it receives item_i as an argument. APPLYXn can optionally receive additional common arguments to pass to all of the expanded applications of MACRO_NAME(..). The expanded application of MACRO_NAME(..) also gets the number i of this item it is applied on, and the total number n of items.

Synopsis

Macro call:

APPLYXn(MACRO_NAME, (AdditionalArgument(s)[, ...]), item_1, ..., item_n)

Expands into:

MACRO_NAME(n, 1, additional_arg_1, [additional_arg_2, [...]] item_1)
MACRO_NAME(n, 2, additional_arg_1, [additional_arg_2, [...]] item_2)
MACRO_NAME(n, 3, additional_arg_1, [additional_arg_2, [...]] item_3)
...
MACRO_NAME(n, n, additional_arg_1, [additional_arg_2, [...]] item_n)

Explanation: In each expanded application of MACRO_NAME(..) it gets: MACRO_NAME(n, i, additional_arg_1, [additional_arg_2, [...]] item_i), where:

• n is the total number of items that APPLYXn got;
• i is the number of the current item;
• additional_arg_1, ..., additional_arg_k are passed (if given to APPLYXn(..)). You can pass to APPLYXn none, single, or more than one additional args. In the last case you should wrap them within parentheses; they'll be automatically stripped-off when sending the args to the MACRO_NAME macro, as will be shown in the following example;
• item_i is the i-th item passed to APPLYXn (after the additional arguments).

Example

#include "applyxn.h"

#define A(T,N,AdditionalArgs,item) \
    C(T,N,AdditionalArgs,item);

APPLYXn(A, (1,2,3), 'a', 'b', 'c', 'd', 'e', 'f')
// Expands to:
// C(6,1,1,2,3,'a'); C(6,2,1,2,3,'b'); C(6,3,1,2,3,'c'); C(6,4,1,2,3,'d'); C(6,5,1,2,3,'e'); C(6,6,1,2,3,'f');
APPLYXn(A, (), 'a', 'b', 'c', 'd', 'e', 'f')
// Expands to:
// C(6,1,,'a'); C(6,2,,'b'); C(6,3,,'c'); C(6,4,,'d'); C(6,5,,'e'); C(6,6,,'f');
APPLYXn(A, 1, 'a', 'b', 'c', 'd', 'e', 'f')
// Expands to:
// C(6,1,1,'a'); C(6,2,1,'b'); C(6,3,1,'c'); C(6,4,1,'d'); C(6,5,1,'e'); C(6,6,1,'f');
APPLYXn(A, , 'a', 'b', 'c', 'd', 'e', 'f')
// Expands to:
// C(6,1,,'a'); C(6,2,,'b'); C(6,3,,'c'); C(6,4,,'d'); C(6,5,,'e'); C(6,6,,'f');

Files

• applyxn.h is actually the sole file that should be #included in order to use APPLYXn(). It supports up to 64 items per call.
• applyxn-generator.py is a python script that generates applyxn.h. It can get an integer as an input which is the maximum number of items that APPLYXn() can get. If you need to support more than 64 items, you can use this script to re-generate applyxn.h accordingly.
• test.c consists a demonstraction of a minimalist usage example.