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>

1 files changed, 41 insertions, 0 deletions

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