ground_truth/libraries/src/NonlinearArithmetic/Internals/ModInternalsNonlinear.dfy

// RUN: %verify "%s"

/*******************************************************************************
 *  Original: Copyright (c) Microsoft Corporation
 *  SPDX-License-Identifier: MIT
 *  
 *  Modifications and Extensions: Copyright by the contributors to the Dafny Project
 *  SPDX-License-Identifier: MIT 
 *******************************************************************************/

module {:options "-functionSyntax:4"} ModInternalsNonlinear {

  /* WARNING: Think three times before adding to this file, as nonlinear
  verification is highly unstable! */

  /* the remainder of 0 divided by an integer is 0 */
  lemma LemmaModOfZeroIsZero(m:int)
    requires 0 < m
    ensures 0 % m == 0
  {
  }

  /* describes fundementals of the modulus operator */
  lemma LemmaFundamentalDivMod(x:int, d:int)
    requires d != 0
    ensures x == d * (x / d) + (x % d)
  {
  }

  /* the remained of 0 divided by any integer is always 0 */
  lemma Lemma0ModAnything()
    ensures forall m: int {:trigger 0 % m} :: m > 0 ==> 0 % m == 0
  {
  }

  /* a natural number x divided by a larger natural number gives a remainder equal to x */
  lemma LemmaSmallMod(x:nat, m:nat)
    requires x < m
    requires 0 < m
    ensures x % m == x
  {
  }

  /* the range of the modulus of any integer will be [0, m) where m is the divisor */
  lemma LemmaModRange(x:int, m:int)
    requires m > 0
    ensures 0 <= x % m < m
  {
  }

}