From 73de311edc5ef3445ea39815156b2163502a2814 Mon Sep 17 00:00:00 2001
From: Romain Goyet <romain@goyet.com>
Date: Mon, 21 Sep 2015 12:05:30 +0200
Subject: [PATCH] [poincare] integer comparison

---
 poincare/include/poincare/integer.h |  2 ++
 poincare/src/integer.cpp            | 17 ++++++++++++++++-
 poincare/test/integer.cpp           |  8 ++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/poincare/include/poincare/integer.h b/poincare/include/poincare/integer.h
index 2655b04ed..6c8e4e690 100644
--- a/poincare/include/poincare/integer.h
+++ b/poincare/include/poincare/integer.h
@@ -19,6 +19,8 @@ class Integer : public Expression {
     // Arithmetic
     Integer operator+(const Integer &other) const;
     Integer operator*(const Integer &other) const;
+
+    bool operator<(const Integer &other) const;
     bool operator==(const Integer &other) const;
 
     /*virtual Expression ** children();
diff --git a/poincare/src/integer.cpp b/poincare/src/integer.cpp
index 6b777f5d8..edc83b5e9 100644
--- a/poincare/src/integer.cpp
+++ b/poincare/src/integer.cpp
@@ -87,8 +87,23 @@ Integer::~Integer() {
 Integer::Integer(native_uint_t * digits, uint16_t numberOfDigits) :
   m_numberOfDigits(numberOfDigits),
   m_digits(digits) {
-  }
+}
 
+// TODO: factor code with "==", they are very similar
+bool Integer::operator<(const Integer &other) const {
+  if (m_numberOfDigits != other.m_numberOfDigits) {
+    return (m_numberOfDigits < other.m_numberOfDigits);
+  }
+  for (uint16_t i = 0; i < m_numberOfDigits; i++) {
+    // Digits are stored most-significant last
+    native_uint_t digit = m_digits[m_numberOfDigits-i-1];
+    native_uint_t otherDigit = other.m_digits[m_numberOfDigits-i-1];
+    if (digit != otherDigit) {
+      return (digit < otherDigit);
+    }
+  }
+  return false;
+}
 
 bool Integer::operator==(const Integer &other) const {
   if (other.m_numberOfDigits != m_numberOfDigits) {
diff --git a/poincare/test/integer.cpp b/poincare/test/integer.cpp
index 2a33f541c..f4fee433b 100644
--- a/poincare/test/integer.cpp
+++ b/poincare/test/integer.cpp
@@ -10,6 +10,14 @@ QUIZ_CASE(poincare_integer) {
   assert(Integer("0b1011") == Integer(11));
 }
 
+QUIZ_CASE(poincare_integer_compare) {
+  assert(Integer(123) < Integer(456));
+  assert(!(Integer(123) < Integer(123)));
+  assert(Integer(123) < Integer("123456789123456789"));
+  assert(Integer("123456789123456788") < Integer("123456789123456789"));
+  assert(!(Integer("123456789123456789") < Integer("123456789123456788")));
+}
+
 QUIZ_CASE(poincare_integer_add) {
   //assert(Integer((uint32_t)0) + Integer((uint32_t)0) == Integer((uint32_t)0));
   assert(Integer(123) + Integer(456) == Integer(579));