From 589f8e2558d008c63892f2345b233e28d889620b Mon Sep 17 00:00:00 2001
From: Olivier Gayot <og@satcom1.com>
Date: Fri, 8 Sep 2017 20:06:38 +0200
Subject: Added the addition of two numbers

We're using the grade school addition method to compute the sum of two
numbers of size n.

Signed-off-by: Olivier Gayot <og@satcom1.com>
---
 number.cpp | 41 +++++++++++++++++++++++++++++++++++++++++
 number.h   |  7 +++++++
 2 files changed, 48 insertions(+)

diff --git a/number.cpp b/number.cpp
index e942cf2..f6f445c 100644
--- a/number.cpp
+++ b/number.cpp
@@ -1,5 +1,46 @@
 #include "number.h"
 
+/* Operations {{{ */
+
+number
+number::operator+(const number &n) const
+{
+    /* We make sure our object is greater than or equal to n. */
+    if (*this < n) {
+        return n.operator+(*this);
+    }
+
+    number result;
+
+    auto it = _operands.cbegin();
+    auto it_n = n._operands.cbegin();
+
+    bool carry = false;
+
+    while (it != _operands.cend()) {
+        const auto n1 = *it;
+        const auto n2 = *it_n;
+
+        result._operands.push_back(n1 + n2 + (carry ? 1 : 0));
+
+        if (carry && (n1 == UINT64_MAX)) {
+            carry = true;
+        } else {
+            carry = ((UINT64_MAX - n1 - (carry ? 1 : 0)) < n2);
+        }
+
+        ++it;
+        ++it_n;
+    }
+
+    if (carry) {
+        result._operands.push_back(1);
+    }
+
+    return result;
+}
+
+/* }}} */
 /* Comparison operators {{{ */
 
 bool
diff --git a/number.h b/number.h
index c508a81..ca5075e 100644
--- a/number.h
+++ b/number.h
@@ -8,6 +8,13 @@ class number {
 public:
     number() = default;
 
+    /**
+     * \brief Return the result of the addition of a number and this number.
+     *
+     * \param n The number to add to this number.
+     */
+    number operator+(const number &n) const;
+
     /**
      * \brief Tells whether the number passed as parameter is strictly less
      * than this number.
-- 
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