Add some comments and TODOs

.clang-format

@@ -1,13 +1,14 @@
 ---
 BasedOnStyle: LLVM
-AllowShortBlocksOnASingleLine: 'true'
+AllowShortBlocksOnASingleLine: false
-AllowShortCaseLabelsOnASingleLine: 'true'
+AllowShortCaseLabelsOnASingleLine: true
-AllowShortFunctionsOnASingleLine: Inline
+AllowShortFunctionsOnASingleLine: None
 AllowShortIfStatementsOnASingleLine: WithoutElse
 AllowShortLambdasOnASingleLine: Inline
-AllowShortLoopsOnASingleLine: 'false'
+AllowShortLoopsOnASingleLine: false
-AlwaysBreakBeforeMultilineStrings: 'true'
+AlwaysBreakBeforeMultilineStrings: true
-IndentWidth: '4'
+AlwaysBreakTemplateDeclarations: true
-ColumnLimit: 100
+IndentWidth: 4
+ColumnLimit: 80
 
 ...

.vscode/launch.json

@@ -5,7 +5,7 @@
     "version": "0.2.0",
     "configurations": [
         {
-            "name": "Debug",
+            "name": "Test",
             "type": "gdb",
             "request": "launch",
             "target": "./vector.out",

README.md

@@ -6,4 +6,7 @@ Run `scons` in the root directory.
 ## Developing
 The `scons` command also generates a `compile_commands.json` which can be used by the VSCodium extension `clangd` for autocompletion, debugging, etc.
 
-Build and run scripts for VSCodium are provided as well.
+Build and run scripts for VSCodium are provided as well.
+
+## Credits
+Catch2 for unit tests: https://github.com/catchorg/Catch2

Vector.cpp

@@ -1,6 +0,0 @@
-#include "Vector.h"
-#include <iostream>
-
-Vector::Vector() {
-    std::cout << "Vector created" << std::endl;
-}

Vector.h

@@ -1,4 +1,155 @@
+#pragma once
+#include <algorithm>
+#include <cassert>
+#include <iostream>
+
+template <class T>
 class Vector {
   public:
-    Vector();
+    // Constructor
+    // If the needed capacity is known, it can be passed; other wise, a default
+    // capacity is reserved.
+    Vector(unsigned int capacity = 10)
+        : capacity(capacity), element_count(0), data(new T[capacity]) {
+    }
+
+    // Copy Constructor
+    Vector(const Vector &other)
+        : capacity(other.capacity), element_count(other.element_count),
+          data(new T[capacity]) {
+        // `std::copy` is used because it is more flexible than `std::memcpy`,
+        // and the compiler will replace it with `memcpy` anyway if appropriate,
+        // so there is no performance loss.
+        std::copy(other.data, other.data + element_count, data);
+    }
+
+    // Move Constructor using the copy-and-swap-idiom
+    Vector(Vector &&other) : data(new T[capacity]) {
+        swap(*this, other);
+    }
+
+    // Copy Assignment Operator using the copy-and-swap-idiom
+    // Since this takes a value rather than a const reference due to
+    // copy-and-swap, this is also the Move Assignment Operator.
+    // This works because we pass-by-value, causing the copy constructor (which
+    // does the actual copying) to be called, and then we swap the resulting
+    // temporary into `this`.
+    Vector &operator=(Vector other) {
+        swap(*this, other);
+
+        return *this;
+    }
+
+    // Destructor
+    ~Vector() {
+        delete[] data;
+    }
+
+    // Bracket Operator for accessing elements
+    T &operator[](unsigned int position) const {
+        return at(position);
+    }
+
+    // Equals Operator: Returns true if the number of elements is identical and
+    // each of these elements are equal
+    bool operator==(const Vector &other) {
+        if (size() != other.size()) return false;
+
+        for (unsigned int i = 0; i < size(); i++) {
+            if (at(i) != other[i]) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    // Swap function for the copy-and-swap idiom.
+    // See also:
+    // https://stackoverflow.com/questions/3279543/what-is-the-copy-and-swap-idiom
+    // The `friend` keyword is used so it is found through ADL.
+    friend void swap(Vector &first, Vector &second) {
+        // Enable ADL (good practice)
+        using std::swap;
+
+        swap(first.capacity, second.capacity);
+        swap(first.element_count, second.element_count);
+        swap(first.data, second.data);
+    }
+
+    void push_back(const T &element) {
+        // TODO: Allocate additional space if needed
+
+        // Use placement new to directly use pre-allocated memory
+        new (data + element_count) T(element);
+        element_count++;
+    }
+
+    void erase(unsigned int position) {
+        assert(position < element_count);
+
+        // Call the destructor on the given element
+        data[position].~T();
+
+        // Copy the other elements forwards
+        std::copy_backward(data + position + 1, data + element_count,
+                           data + element_count - 1);
+
+        element_count--;
+
+        // TODO: Consider deallocating memory if a certain threshold was reached
+    }
+
+    // Returns the number of elements in the vector, regardless of the actually
+    // reserved memory.
+    unsigned int size() const {
+        return element_count;
+    }
+
+    // Returns the number of elements which could be in the vector using the
+    // currently allocated memory, regardless of how many of these slots are
+    // currently actually used.
+    unsigned int length() const {
+        return capacity;
+    }
+
+    // Returns a reference to the element at the given position
+    T &at(unsigned int position) const {
+        assert(position < element_count);
+        return data[position];
+    }
+
+    // Expand the capacity of the vector by the given addition
+    void reserve(unsigned int addition) {
+        // TODO: Actual memory allocation
+        capacity += addition;
+    }
+
+    // Resize the size of the vector to the given new_size
+    // If this decreases the size, some elements are deleted
+    // If this increases the size, some default-constructed elements are added
+    void resize(unsigned int new_size) {
+        int difference = new_size - size();
+
+        if (difference > 0) {
+            // TODO: Reserve more space if needed
+            // Add additional default-constructed items
+            for (int i = 0; i < difference; i++) {
+                data[element_count + i] = T();
+            }
+        } else if (difference < 0) {
+            // Call the destructor on all excess items
+            for (int i = -1; i > difference; i--) {
+                data[element_count + i].~T();
+            }
+            // TODO: Consider deallocating space
+        }
+
+        element_count += difference;
+    }
+
+  private:
+    T *data;
+    unsigned int element_count;
+    unsigned int capacity;
 };

main.cpp

@@ -1,6 +0,0 @@
-#include "Vector.h"
-#include <iostream>
-
-int main() {
-    Vector vector;
-}

test.cpp

@@ -0,0 +1,229 @@
+#include "Vector.h"
+#include <iostream>
+
+#define CATCH_CONFIG_MAIN // This tells Catch to provide a main() - only do this
+                          // in one cpp file
+#include "catch_amalgamated.hpp"
+
+SCENARIO("Vector size and length are correct", "[vector]") {
+    Vector<int> v(20);
+    v.push_back(1);
+
+    REQUIRE(v.size() == 1);
+    REQUIRE(v.length() == 20);
+}
+
+SCENARIO("The bracket operator returns the correct element", "[vector]") {
+    Vector<int> v(20);
+    v.push_back(1);
+    v.push_back(2);
+    v.push_back(3);
+
+    REQUIRE(v[1] == 2);
+}
+
+SCENARIO("Equality is returned correctly", "[vector]") {
+    GIVEN("Two vectors with the same items") {
+        Vector<int> v1;
+        Vector<int> v2;
+
+        v1.push_back(1);
+        v2.push_back(1);
+
+        v1.push_back(5);
+        v2.push_back(5);
+
+        REQUIRE(v1.size() == 2);
+        REQUIRE(v2.size() == 2);
+
+        WHEN("Comparing them") {
+            bool equals = v1 == v2;
+
+            THEN("The result should be true") {
+                REQUIRE(equals);
+            }
+        }
+    }
+
+    GIVEN("Two vectors with different items") {
+        Vector<int> v1;
+        Vector<int> v2;
+
+        v1.push_back(1);
+        v2.push_back(2);
+
+        v1.push_back(5);
+        v2.push_back(5);
+
+        REQUIRE(v1.size() == 2);
+        REQUIRE(v2.size() == 2);
+
+        WHEN("Comparing them") {
+            bool equals = v1 == v2;
+
+            THEN("The result should be false") {
+                REQUIRE_FALSE(equals);
+            }
+        }
+    }
+}
+
+SCENARIO("Erasing an item removes it and moves the following ones forward",
+         "[vector]") {
+    GIVEN("Two vectors with almost identical items") {
+        Vector<int> v1;
+        Vector<int> v2;
+
+        v1.push_back(1);
+        v2.push_back(1);
+
+        v1.push_back(2);
+        v2.push_back(5);
+
+        v1.push_back(5);
+
+        v1.push_back(10);
+        v2.push_back(10);
+
+        REQUIRE(v1.size() == 4);
+        REQUIRE(v2.size() == 3);
+
+        WHEN("Comparing them") {
+            bool equals = v1 == v2;
+
+            THEN("The result should be false") {
+                REQUIRE_FALSE(equals);
+            }
+        }
+
+        WHEN("Erasing the different item") {
+            v1.erase(1);
+            bool equals = v1 == v2;
+
+            THEN("The result should be true") {
+                REQUIRE(equals);
+            }
+        }
+    }
+}
+
+SCENARIO("Copy Assignment", "[vector]") {
+    GIVEN("Two vectors with identical items") {
+        Vector<int> v1;
+        Vector<int> v2;
+
+        v1.push_back(1);
+        v2.push_back(1);
+
+        v1.push_back(5);
+        v2.push_back(5);
+
+        REQUIRE(v1.size() == 2);
+        REQUIRE(v2.size() == 2);
+
+        WHEN("Copy assigning the second vector to a third vector") {
+            Vector<int> v3;
+            v3 = v2;
+
+            THEN("All vectors should be identical") {
+                bool equals = v1 == v2 && v2 == v3 && v1 == v3;
+                REQUIRE(equals);
+            }
+        }
+    }
+}
+
+SCENARIO("Move Assignment", "[vector]") {
+    GIVEN("Two vectors with identical items") {
+        Vector<int> v1;
+        Vector<int> v2;
+
+        v1.push_back(1);
+        v2.push_back(1);
+
+        v1.push_back(5);
+        v2.push_back(5);
+
+        REQUIRE(v1.size() == 2);
+        REQUIRE(v2.size() == 2);
+
+        WHEN("Move assigning the second vector to a third vector") {
+            Vector<int> v3;
+            v3 = std::move(v2);
+
+            THEN("The first and third vector should be identical") {
+                bool equals = v1 == v3;
+                REQUIRE(equals);
+            }
+        }
+    }
+}
+
+SCENARIO("Reserve additional space", "[vector]") {
+    GIVEN("A vector with a given length") {
+        Vector<int> v(5);
+
+        REQUIRE(v.length() == 5);
+
+        WHEN("Reserving additional space") {
+            v.reserve(10);
+
+            THEN("The length has increased accordingly") {
+                REQUIRE(v.length() == 15);
+            }
+        }
+    }
+}
+
+SCENARIO("Resizing a vector", "[vector]") {
+    GIVEN("A vector with 3 items") {
+        Vector<int> v;
+
+        v.push_back(1);
+        v.push_back(2);
+        v.push_back(3);
+
+        Vector<int> target;
+
+        target.push_back(1);
+        target.push_back(2);
+        target.push_back(3);
+        target.push_back(0);
+        target.push_back(0);
+
+        WHEN("Resizing to 5") {
+            v.resize(5);
+
+            THEN("The size should be 5") {
+                REQUIRE(v.size() == 5);
+            }
+
+            THEN("2 new default items should've been added") {
+                bool equals = v == target;
+                REQUIRE(equals);
+            }
+        }
+
+        WHEN("Resizing to 1") {
+            v.resize(1);
+
+            THEN("The size should be 1") {
+                REQUIRE(v.size() == 1);
+            }
+
+            THEN("The remaining element should be correct") {
+                REQUIRE(v[0] == 1);
+            }
+
+            THEN("Adding the elements again produces the same result again") {
+                v.push_back(2);
+                v.push_back(3);
+                v.push_back(0);
+                v.push_back(0);
+
+                bool equals = v == target;
+                REQUIRE(equals);
+            }
+        }
+    }
+}