Statically-defined tuples in C

ctuple.h

/* Basic tuple definitions */

#define ctuple1(a) union { struct { a hd; }; struct { a idx0; }; }
#define ctuple2(a, b) union { struct { a hd; ctuple1(b) tl; }; \
                              struct { a idx0; b idx1; }; }

#define ctuple3(a, b, c) union { struct { a hd; ctuple2(b, c) tl; }; \
                                 struct { a idx0; b idx1; c idx2; }; }

#define ctuple4(a, b, c, d) union { struct { a hd; ctuple3(b, c, d) tl; }; \
                                    struct { a idx0; b idx1; c idx2; d idx3; }; }

#define ctuple5(a, b, c, d, e) union { struct { a hd; ctuple4(b, c, d, e) tl; }; \
                                       struct { a idx0; b idx1; c idx2; d idx3; e idx4; }; }

/* Scheme-style accessors */

#define car(tuple)    tuple.hd
#define cdr(tuple)    tuple.tl
#define caar(tuple)   tuple.hd.hd
#define cadr(tuple)   tuple.hd.tl
#define cdar(tuple)   tuple.tl.hd
#define cddr(tuple)   tuple.tl.tl
#define caaar(tuple)  tuple.hd.hd.hd
#define caadr(tuple)  tuple.hd.hd.tl
#define cadar(tuple)  tuple.hd.tl.hd
#define caddr(tuple)  tuple.hd.tl.tl
#define cdaar(tuple)  tuple.tl.hd.hd
#define cdadr(tuple)  tuple.tl.hd.tl
#define cddar(tuple)  tuple.tl.tl.hd
#define cdddr(tuple)  tuple.tl.tl.tl
#define caaaar(tuple) tuple.hd.hd.hd.hd
#define caaadr(tuple) tuple.hd.hd.hd.tl
#define caadar(tuple) tuple.hd.hd.tl.hd
#define caaddr(tuple) tuple.hd.hd.tl.tl
#define cadaar(tuple) tuple.hd.tl.hd.hd
#define cadadr(tuple) tuple.hd.tl.hd.tl
#define caddar(tuple) tuple.hd.tl.tl.hd
#define cadddr(tuple) tuple.hd.tl.tl.tl
#define cdaaar(tuple) tuple.tl.hd.hd.hd
#define cdaadr(tuple) tuple.tl.hd.hd.tl
#define cdadar(tuple) tuple.tl.hd.tl.hd
#define cdaddr(tuple) tuple.tl.hd.tl.tl
#define cddaar(tuple) tuple.tl.tl.hd.hd
#define cddadr(tuple) tuple.tl.tl.hd.tl
#define cdddar(tuple) tuple.tl.tl.tl.hd
#define cddddr(tuple) tuple.tl.tl.tl.tl

tupletest.c

#include <stdbool.h>
#include <stdio.h>

#include "ctuple.h"

int main(int argc, char** argv)
{
    ctuple2(int, int) vec = {3, 4};

    ctuple2(int, ctuple2(float, char*)) test = {3, {3.f, "hello"}};
    test.hd = 3.f;

    ctuple4(int, float, char*, bool) tuple4 = {3, 3.14, "tuples!", true};

    printf("DIRECT ACCESS\n");
    printf("The int value is %d\n", tuple4.idx0);
    printf("The float value is %f\n", tuple4.idx1);
    printf("The string value is %s\n", tuple4.idx2);
    printf("The bool value is %s\n\n", tuple4.idx3 ? "true" : "false");

    printf("LIST-STYLE ITERATION\n");
    printf("The int value is %d\n", tuple4.hd);
    printf("The float value is %f\n", tuple4.tl.hd);
    printf("The string value is %s\n", tuple4.tl.tl.hd);
    printf("The bool value is %s\n\n", tuple4.tl.tl.tl.hd ? "true" : "false");

    printf("SCHEME-STYLE ACCESSORS\n");
    printf("The int value is %d\n", car(tuple4));
    printf("The float value is %f\n", cdar(tuple4));
    printf("The string value is %s\n", cddar(tuple4));
    printf("The bool value is %s\n\n", cdddar(tuple4) ? "true" : "false");

    ctuple4(int, ctuple2(float, float), char*, bool) tuple2d = {3, 3.14, 3.4, "tuples!", true};
    printf("idx %d x %f y %f\n", tuple2d.idx0, tuple2d.idx1.idx0, tuple2d.idx1.idx1 );

    return 0;
}