ex 3-3 (the c programming language)

expand.c

#include <stdio.h>

void expand (char s1[], char s2[])
{
    int i = 0, n, x = 0;

       if (s1[i] >= 'a' && s1[i + 1] == '-' && s1[i + 2] <= 'z')  {

            if (s1[i + 3] == '-' && (s1[i + 2] >= s1[i] && s1[i + 2] <= s1[i + 4]) && s1[i + 4] <= 'z') {
                for (n = s1[i]; n <= s1[i + 4]; ++n, ++x)
                    s2[x] = n;

                s2[x] = '\0';
                return;
            }
            else if (s1[i + 3] >= '0' && s1[i + 4] == '-' && s1[i + 5] <= '9') {
                for (n = s1[i]; n <= s1[i + 2]; ++n, ++x)
                    s2[x] = n;

                s2[x++] = '\n';

                for (n = s1[i + 3]; n <= s1[i + 5]; ++n, ++x)
                    s2[x] = n;

                s2[x] = '\0';

                return;
            }

            for (n = s1[i]; n <= s1[i + 2]; ++n, ++x)
                s2[x] = n;

            s2[x] = '\0';

            return;

        }

     if (s1[i] == '-' && s1[i + 1] >= 'a' && s1[i + 2] == '-' && s1[i + 3] <= 'z') {
        for (n = s1[i + 1]; n <= s1[i + 3]; ++n, ++x)
            s2[x] = n;

        s2[x] = '\0';
     }

}

int main ()
{
    char str[100];

    expand("-b-t", str);

    printf ("%s\n", str);

    return 0;
}