GSP: Print integer values with a specific scale

print_int.c

#include <stdint.h>
#include <stdio.h>

void print_int(const int64_t v) {
    const bool neg = v < 0;
    uint64_t pv = neg ? -v : v;
    
    // convert into digit characters
    static const size_t DIGITS_LENGTH = 19;
    char digits[DIGITS_LENGTH];
    size_t end = 0;
    for (size_t i = 0; i < DIGITS_LENGTH; i++) {
        if (pv < 10) {
            digits[i] = pv;
            end = i;
            break;
        }
        
        digits[i] = pv % 10;
        pv /= 10;
    }
    
    // print to stdout
    if (neg) putchar('-');
    if (end == 0) putchar('0');
    
    for (int i = end; i >= 0; i--) {
        if (i == 0) putchar(',');
        putchar(digits[i] + '0');
    }
}

int main() {
    print_int(-11); putchar('\n');
    print_int(-10); putchar('\n');
    print_int(-9);  putchar('\n');
    print_int(-1);  putchar('\n');
    print_int(0);   putchar('\n');
    print_int(1);   putchar('\n');
    print_int(9);   putchar('\n');
    print_int(10);  putchar('\n');
    print_int(11);  putchar('\n');
    print_int(19);  putchar('\n');
    print_int(111); putchar('\n');
}