From 699010484f102ef347be5fd9219da86ea4319d20 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89milie=20Feral?= <emilie.feral@numworks.com>
Date: Fri, 1 Jun 2018 14:52:38 +0200
Subject: [PATCH] [solver] Equation: fix edge case: if the equation was
 simplified because always true, the standard form must be 0

---
 apps/solver/equation.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/apps/solver/equation.cpp b/apps/solver/equation.cpp
index ee3ae35b0..4468d24e2 100644
--- a/apps/solver/equation.cpp
+++ b/apps/solver/equation.cpp
@@ -37,7 +37,14 @@ void Equation::tidy() {
 
 Expression * Equation::standardForm(Context * context) const {
   if (m_standardForm == nullptr) {
-    m_standardForm = static_cast<const Equal *>(expression(context))->standardEquation(*context);
+    Expression * e = expression(context);
+    if (e->type() == Expression::Type::Equal) {
+      m_standardForm = static_cast<const Equal *>(e)->standardEquation(*context);
+    } else {
+      // The equality was reduced which means the equality was always true.
+      assert(e->type() == Expression::Type::Rational && static_cast<Rational *>(e)->isOne());
+      m_standardForm = new Rational(0);
+    }
   }
   return m_standardForm;
 }