String Literal with Array Subscript Trick

This is a cool trick I just found out recently.

If you have a string literal such as "abcdef", you can interpret that as an array and use the '[]' operator to get the correct character from the string.

For example:

int main() {
    for (int i = 9; i >= 0; i--) {
        cout << "abcdefghij"[i];
    }
    cout << endl;
}

That will print out "jihgfedcba".


Now knowing this trick (as well as some other minor changes), we can omit a few lines from our hexToString() function in my previous article.

string toHexString(u32 value) {
    char str9[9] = {'0'}; // '0' char followed by null bytes
    for (int i = 7, pos = 0; i >= 0; i--) {
        char dig = (value>>(i*4))&0xf;
        if (!dig && !pos) continue;
        str9[pos++] = "0123456789abcdef"[dig];
    }
    return string(str9);
}