Question

Here is a lisp procedure that simply adds ‘a’ to the absolute value of ‘b’:

(define (a-plus-abs-b a b)
  ((if (> b 0) + -) a b))

I think this is beautiful, and I am trying to find the best way of writing this in JavaScript. But my JavaScript code is not beautiful:

var plus = function(a,b) {
    return a + b;
};

var minus = function(a,b) {
    return a - b;
};

var aPlusAbsB = function(a,b) {
    return (b > 0 ? plus : minus)(a,b);
}

The main problem is that I cannot use the + and - symbols as references to the functions they really represent as I can with lisp. Can anyone come up with a more graceful way of doing something like this, or have I hit a language boundary?

Obviously, I can do this:

var aPlusAbsB = function(a,b) {
    return a + Math.abs(b);
}

, but this is more of a thought experiment than a pragmatic question.

Is there any way I can get reference to the core functions in the JavaScript language just as if they were user-defined?

Answer 1

It’s a very cool idea – would be great for evaluating mathematical expressions but you simply can’t set an operator (or the logic behind it) to a variable. Sorry 🙂