From 93b5a3f63a837691d244cf534254bf82d2021f7a Mon Sep 17 00:00:00 2001
From: Hugo Saint-Vignes <hugo.saint-vignes@numworks.com>
Date: Thu, 22 Oct 2020 10:54:33 +0200
Subject: [PATCH] [poincare] Handle equal negative numbers in GCD LCM

Change-Id: Ia46966270418a339f8a37e8a1971a7f7dd046034
---
 poincare/src/arithmetic.cpp      | 23 +++++++++++++----------
 poincare/test/simplification.cpp |  2 ++
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/poincare/src/arithmetic.cpp b/poincare/src/arithmetic.cpp
index 673195469..e65879385 100644
--- a/poincare/src/arithmetic.cpp
+++ b/poincare/src/arithmetic.cpp
@@ -9,13 +9,13 @@ Integer Arithmetic::GCD(const Integer & a, const Integer & b) {
   if (a.isOverflow() || b.isOverflow()) {
     return Integer::Overflow(false);
   }
-  if (a.isEqualTo(b)) {
-    return a;
-  }
   Integer i = a;
   Integer j = b;
   i.setNegative(false);
   j.setNegative(false);
+  if (i.isEqualTo(j)) {
+    return i;
+  }
   do {
     if (i.isZero()) {
       return j;
@@ -35,14 +35,17 @@ Integer Arithmetic::LCM(const Integer & a, const Integer & b) {
   if (a.isZero() || b.isZero()) {
     return Integer(0);
   }
-  if (a.isEqualTo(b)) {
-    return a;
+  Integer i = a;
+  Integer j = b;
+  i.setNegative(false);
+  j.setNegative(false);
+  if (i.isEqualTo(j)) {
+    return i;
   }
-  /* Using LCM(a,b) = a*(b/GCD(a,b)). Knowing that GCD(a, b) divides b,
-   * division is performed before multiplication to be more efficient. */
-  Integer signResult = Integer::Multiplication(a, Integer::Division(b, GCD(a, b)).quotient);
-  signResult.setNegative(false);
-  return signResult;
+  /* Using LCM(i,j) = i*(j/GCD(i,j)). Knowing that GCD(i, j) divides j, and that
+   * GCD(i,j) = 0 if and only if i == j == 0, which would have been escaped
+   * before. Division is performed before multiplication to be more efficient.*/
+  return Integer::Multiplication(i, Integer::Division(j, GCD(i, j)).quotient);
 }
 
 int Arithmetic::GCD(int a, int b) {
diff --git a/poincare/test/simplification.cpp b/poincare/test/simplification.cpp
index fda691e27..28a406092 100644
--- a/poincare/test/simplification.cpp
+++ b/poincare/test/simplification.cpp
@@ -727,10 +727,12 @@ QUIZ_CASE(poincare_simplification_function) {
   assert_parsed_expression_simplify_to("gcd(123,278)", "1");
   assert_parsed_expression_simplify_to("gcd(11,121)", "11");
   assert_parsed_expression_simplify_to("gcd(56,112,28,91)", "7");
+  assert_parsed_expression_simplify_to("gcd(-32,-32)", "32");
   assert_parsed_expression_simplify_to("im(1+5×𝐢)", "5");
   assert_parsed_expression_simplify_to("lcm(123,278)", "34194");
   assert_parsed_expression_simplify_to("lcm(11,121)", "121");
   assert_parsed_expression_simplify_to("lcm(11,121, 3)", "363");
+  assert_parsed_expression_simplify_to("lcm(-32,-32)", "32");
   assert_parsed_expression_simplify_to("√(4)", "2");
   assert_parsed_expression_simplify_to("re(1+5×𝐢)", "1");
   assert_parsed_expression_simplify_to("root(4,3)", "root(4,3)");