Find words like "coffee" (#C0FFEE) which can be written as hexadecimal number.

c0ffee.c

// rewrite of Haskell to C
// from https://github.com/mitsuji/c0ffee

// Find words like "coffee" (#C0FFEE) which can be written as hexadecimal number.
// I made a couple of careless pointer errors
// Proof I should use Haskell more, and C less?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define true 1
#define false 0

int hexlike(unsigned char c)
{
    return (
        ((unsigned)c-'0')  < 10 || 
        ((unsigned)(c | 32)-'a') < 6 || 
        c == 'I' ||
        c == 'O' ||
        c == 'S' ||
        c == 'Z' ||
        c == 'l' ||
        c == 'o' ||
        c == 'q' ||
        c == 's' 
        );
}

int line_is_hexlike_word(char *p)
{
    while(hexlike(*p++)) {
        if (!*p) return true;
    }
    return false;
}

// WARNING: MUTATES ARG!
char* conv(char *line)
{
    static char *s = "IOSZloqsz";
    static char *r = "105210952";
    for (char *pl = line; *pl; pl++)
    {
        char *ps = strchr(s, *pl);
        if (ps) {
            *pl = r[ps-s]; // POKE the translated char back into source buffer
        }
    }
    return line;
}      

int main() {
    // buffer overflow still possible, no matter how big you make this! :
    char buf[65536]; 
    int c;
    while(gets(buf)) {
        if (line_is_hexlike_word(buf)) {
            printf("%-15s", buf);
            // must be separate call, due to mutation of buf by conv():
            printf(" %s\n", conv(buf)); 
        }
    }
}