# teaching machines

## CS 330 Lecture 23 – Matrix/vector and templates

March 30, 2012 by . Filed under cs330, lectures, spring 2012.

### Agenda

• operator<<
• operator()
• named constructor pattern
• templates

### Code

#### Vector.h

#ifndef VECTOR_H
#define VECTOR_H

#include <iostream>
#include <fstream>

class Vector2 {
public:
Vector2();
Vector2(float x, float y);

// write a subscript operator
float& operator[](int index);

const float& operator[](int index) const;

Vector2 operator+(const Vector2& other);

// overload a print operator

private:
float x;
float y;
};

std::ostream& operator<<(std::ostream& out,
const Vector2& v);

#endif


#### Vector.cpp

#include <cassert>
#include "Vector.h"

Vector2::Vector2() :
x(0.0f),
y(0.0f) {
}

Vector2::Vector2(float x, float y) :
x(x),
y(y) {
}

float& Vector2::operator[](int index) {
assert(index >= 0 && index <= 1);
return index == 0 ? x : y;
}

const float& Vector2::operator[](int index) const {
assert(index >= 0 && index <= 1);
return index == 0 ? x : y;
}

Vector2 Vector2::operator+(const Vector2& other) {
return Vector2(x + other.x, y + other.y);
}

std::ostream& operator<<(std::ostream& out,
const Vector2& v) {
out << v[0] << "," << v[1];
}


#### drawer.cpp

#include <cmath>
#include <iostream>

#include "Matrix.h"
#include "Vector.h"

int main() {
Matrix2 transform;
float radians = 60.0f * 3.14159f / 180.0f;
transform(0, 0) = cos(radians);
transform(0, 1) = -sin(radians);
transform(1, 0) = sin(radians);
transform(1, 1) = cos(radians);
transform(0, 2) = 0.0f;
transform(1, 2) = 0.0f;
transform(2, 0) = 0.0f;
transform(2, 1) = 0.0f;
transform(2, 2) = 1.0f;
Vector2 point(1.0f, 0.0f);

for (int i = 0; i < 6; ++i) {
point = transform * point;
std::cout << point << std::endl;
}

/* Vector2 point2(1.0f, 2.0f); */
/* Vector2 sum = point + point2; */
/* Vector2 sum = point.operator+(point2); */
/* std::cout << "sum[0]: " << sum[0] << std::endl; */
/* std::cout << "sum[1]: " << sum[1] << std::endl; */
/* std::cout << "sum: " << sum << std::endl; */

/* std::cout << "point[0]: " << point[0] << std::endl; */
/* std::cout << "point[1]: " << point[1] << std::endl; */

/* point[0] = 11.0f; */

/* std::cout << "point[0]: " << point[0] << std::endl; */
/* std::cout << "point[1]: " << point[1] << std::endl; */

/* point[0] // point.getX() */
/* point[1] // point.getY() */
}


### Haiku

Typeless languages.
Puzzles whose pieces don’t lock.
Pain makes a picture.