Functionally Functional

How do you declare/define a function in REBOL? There has to be some kind of keyword or specific definition syntax for that purpose, right? Nope, I tell you! Nope!

First, let's take a look at some other languages. In C you define a function by sticking to a specific syntax (There is a subtle difference between declaring and defining a function, but let's not think about that right now). Here's an example:

int say_number(int number) {
    printf("%d\n", number);
    return number;
}

Javascript has the function keyword for declaring functions:

function say_number(number) {
    document.write(number);
    return number;
}

The Javascript function keyword can also be used for declaring anonymous functions:

var say_number = function (number) {
    document.writeln(number);
    return number;
}

In REBOL, all functions, and I mean all functions, are anonymous. So, defining a function is like using the Javascript keyword then? No, not quite. Here's the REBOL version:

say-number: func [number] [
    print number
    number
]

I know what you're thinking. You're thinking that func sure looks like a keyword! It's not, I assure you. The func symbol is just a symbol that has been bound to a function. A function that creates functions from its two parameters: a list of parameter symbols and a list of data representing the body of the function.

So, let me reiterate; REBOL uses a function to define functions. I know, right? I'm sure it's like totally blowing your mind right now!

Comments: 2 Tags: REBOL