quo_mod.c

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/* SPDX-License-Identifier: MIT */
#include "quo_mod.h"
 
struct quo_mod quo_mod(int x, int y) {
  /*
   * Compute modulus using C's % operator. Note that C's % operator will yield
   * negative results when the numerator is negative.
   */
  int mod = x % y;
 
  /* Adjust negative modulus to be positive. Ensures that:
   *
   *    0 <= mod < y    when y > 0
   *    y < mod <= 0    when y < 0
   *
   * This matches Lua's modulo operator behaviour.
   */
  if (mod != 0 && (mod ^ y) < 0) {
    mod += y;
  }
 
  /*
   * Returns a quo_mod structure by casting an initialiser. Is this portable?
   */
  return (struct quo_mod){.quo = (x - mod) / y, .mod = mod};
}