[COFF] Re: Maximum Array Sizes in 16 bit C

[Ralph Corderoy <ralph@inputplus.co.uk>]

Hi Doug,

> int base[N][N+2];
> #define binom(n,i) base[n][(i)+1]

Thanks for the interesting prompt.  I've been having a think about it
along the lines of sliding the ints in memory.

Have you considered having a single dimension of ints and then accessing
them as if a two-dimensional array, with [0][0] being offset?

    $ cat offset.c
    #include <stdio.h>

    #define N 4  // N×N values
    #define L 3  // L columns of 0 to the left
    #define U 2  // U columns of 0 upwards

    int main()
    {
        char m[(U + N) * (L + N)] =
            "abcdefg"
            "hijklmn"
            "opq+BCD"  // The '+' is a[0][0].
            "rstEFGH"
            "uvwIJKL"
            "xyzMNOP";
        char (*a)[L + N] = (char (*)[L + N])&m[U * (L + N) + L];

        for (int y = -U; y < N; y++) {
            if (!y)
                putchar('\n');

            for (int x = -L; x < N; x++) {
                if (!x)
                    putchar(' ');

                putchar(a[y][x]);  // y,x relative to ‘+’
            }
            putchar('\n');
        }
    }
    $ gcc -Wall -Wextra -Werror offset.c
    $ ./a.out
    abc defg
    hij klmn

    opq +BCD
    rst EFGH
    uvw IJKL
    xyz MNOP
    $

-- 
Cheers, Ralph.