Add increment and decrement operators

include/BigInt.hpp

@@ -65,10 +65,10 @@ class BigInt {
         BigInt& operator%=(const std::string&);   // TODO
 
         // Increment and decrement operators:
-        BigInt& operator++();   // pre-increment    TODO
-        BigInt& operator--();   // pre-decrement    TODO
-        BigInt operator++(int); // post-increment   TODO
-        BigInt operator--(int); // post-decrement   TODO
+        BigInt& operator++();       // pre-increment
+        BigInt& operator--();       // pre-decrement
+        BigInt operator++(int);     // post-increment
+        BigInt operator--(int);     // post-decrement
 
         // Relational operators:
         bool operator<(const BigInt&) const;

include/operators/increment_decrement.hpp

@@ -0,0 +1,70 @@
+/*
+    ===========================================================================
+    Increment and decrement operators
+    ===========================================================================
+*/
+
+#ifndef BIG_INT_INCREMENT_DECREMENT_OPERATORS_HPP
+#define BIG_INT_INCREMENT_DECREMENT_OPERATORS_HPP
+
+#include "BigInt.hpp"
+#include "constructors/constructors.hpp"
+#include "operators/assignment.hpp"
+#include "operators/arithmetic_assignment.hpp"
+#include "operators/binary_arithmetic.hpp"
+
+
+/*
+    Pre-increment
+    -------------
+    ++BigInt
+*/
+
+BigInt& BigInt::operator++() {
+    *this += 1;
+
+    return *this;
+}
+
+
+/*
+    Pre-decrement
+    -------------
+    --BigInt
+*/
+
+BigInt& BigInt::operator--() {
+    *this -= 1;
+
+    return *this;
+}
+
+
+/*
+    Post-increment
+    --------------
+    BigInt++
+*/
+
+BigInt BigInt::operator++(int) {
+    BigInt temp = *this;
+    *this += 1;
+
+    return temp;
+}
+
+
+/*
+    Post-decrement
+    --------------
+    BigInt--
+*/
+
+BigInt BigInt::operator--(int) {
+    BigInt temp = *this;
+    *this -= 1;
+
+    return temp;
+}
+
+#endif  // BIG_INT_INCREMENT_DECREMENT_OPERATORS_HPP