boppi/util/object-oriented-poc.boppi

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/**
* Proof of concept for Object-Oriented Programming in Boppi.
* Note that this is a very basic notion of OO that only includes private
* members. It does not support type checking, inheritance or public members.
* It requires a tremendous amount of boilerplate to work without proper
* tuples, parametrization or OO class syntax.
*/
//Declaring dummy functions for type aliases because Boppi disallows
//the use of Void directly in a type.
function intToVoid(int a) 0;
function int voidToInt() 0;
function class() 0;
//Class declaration whose sole purpose is to make the code look better.
//`Rectangle` type checks with every other `()->Void` type.
var class Rectangle;
//Helpers for making methods available outside their closure (the function
//references should be passed via a return value if tuples were supported)
//Assigning them immediately to suppress warnings.
var voidToInt _getWidth; _getWidth := voidToInt;
var intToVoid _setWidth; _setWidth := intToVoid;
var voidToInt _getHeight; _getHeight := voidToInt;
var intToVoid _setHeight; _setHeight := intToVoid;
var voidToInt _getArea; _getArea := voidToInt;
//Wrappers to make a `getWidth()` call less of an eyesore and allow you
//to nest these calls without overriding the target closure in between
function int getWidth (Rectangle rect) { rect();_getWidth() };
function setWidth (Rectangle rect, int width) { rect();_setWidth(width) };
function int getHeight(Rectangle rect) { rect();_getHeight() };
function setHeight(Rectangle rect, int height) { rect();_setHeight(height) };
function int getArea (Rectangle rect) { rect();_getArea() };
//A class definition looks decent apart from the bind function to expose
//the class methods. You can even add constructor arguments to your liking.
function Rectangle newRectangle() {
var int width;
var int height;
function int getWidth()
width;
function setWidth(int newWidth) {
width := newWidth;
};
function int getHeight()
height;
function setHeight(int newHeight) {
height := newHeight;
};
function int getArea()
width*height;
function bind() {
_getWidth := getWidth;
_setWidth := setWidth;
_getHeight := getHeight;
_setHeight := setHeight;
_getArea := getArea;
};
bind
};
//Time to use the class
var Rectangle a; a := newRectangle();
var Rectangle b; b := newRectangle();
setWidth(a, 4);
setWidth(b, getWidth(a)+2);
setHeight(b, 3);
print(getArea(b));