How to get character's position in alphabet in C language?

Question

Is there a quick way to retrieve given character\'s position in the english alphabet in C?

Something like:

int position = get_position(\'g\');
         


        

Answer 1

This will work with EBCDIC and is case-insensitive:

#include 
#include 
#include 

int getpos (char c)
{
    int pos;
    const char * alphabet = "abcdefghijklmnopqrstuvwxyz";
    const char * found;

    c = tolower ((unsigned char)c);
    found = strchr (alphabet, c);
    pos = found - alphabet;
    if (!found)
        pos = 0;
    else if (pos == 26)
        pos = 0;
    else
        pos++;
    return pos;
}

int main ()
{
    char tests[] = {'A', '%', 'a', 'z', 'M', 0};
    char * c;
    for (c = tests; *c; c++) {
        printf ("%d\n", *c - 'a' + 1);
        printf ("%d\n", getpos (*c));
    }
    return 0;
}

See http://codepad.org/5u5uO5ZR if you want to run it.