Coffeescript tree extends class not working

Question

I need to create a tree that, for example CALCULATE 2 numbers. I do in coffee script, who connvert javascript due to extend class.

class Expression

	@Evaluate = -> 0

    

class Const extends Expression

	constructor: (value)->

  

class BinaryOperation extends Expression

	constructor: (L, R)->

  

class Add extends BinaryOperation

	@Evaluate = -> L.Evaluate() + R.Evaluate();



expr = new Add(new Const(10), new Const(10));

alert(expr.Evaluate())

Demo: https://jsfiddle.net/f3ry/D9kBP/24/
Thanks.

Answer 1

Your problem is a combination of syntax errors and a misunderstanding of how subclassing works. This should get you there:

class Expression
    Evaluate: () -> 0

class Const extends Expression
    constructor: (@value) ->
    Evaluate: () -> @value

class BinaryOperation extends Expression
    constructor: (@L, @R)->

class Add extends BinaryOperation
    Evaluate: -> @L.Evaluate() + @R.Evaluate();

expr = new Add(new Const(10), new Const(10));
alert(expr.Evaluate())

Adding the @ to the constructor parameter sets it as a property of the newly created object. Overriding the Evaluate method allows the operations to be performed. Link to example.

Coffeescript tree extends class not working

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