From OCaml to Javascript

[Jon Harrop]

I'm trying to grok Javascript. As my background is functional programming
languages, all the higher-order functions, currying and so forth are easy
but I've no idea how to express sum types and pattern matches.

Is there a resource to teach the (tiny minority!) of people like me
Javascript?

How do you translate the following symbolic simplifier into Javascript, for
example:

http://www.codecodex.com/wiki/index.php?title=Derivative

 

[Thomas 'PointedEars' Lahn]

I'm trying to grok Javascript. As my background is functional programming
languages, all the higher-order functions, currying and so forth are easy
but I've no idea how to express sum types and pattern matches.

This may surprise you, but ECMAScript implementations include features of
functional languages.

http://javascript.crockford.com/javascript.html

Is there a resource to teach the (tiny minority!) of people like me
Javascript?

This newsgroup? Maybe one of the many resources linked in its FAQ?

How do you translate the following symbolic simplifier into Javascript, for
example:

http://www.codecodex.com/wiki/index.php?title=Derivative

I don't know yet, but please tell us when you got it.


PointedEars

 

[Jon Harrop]

I don't know yet, but please tell us when you got it.

I think I've made some progress. If you take the minimal OCaml example:

# let rec ( +: ) f g = match f, g with
| `Int 0, f | f, `Int 0 -> f
| f, `Add(g, h) -> f +: g +: h
| f, g -> `Add(f, g);;
val ( +: ) : ([> `Add of 'a * 'a | `Int of int ] as 'a) -> 'a -> 'a = <fun>

Then the polymorphic variant type that OCaml inferred is equivalent to a
class hierarchy in JavaScript, which must be something like:

// Equivalent to `Add
function Add(f, g) {
this.f = f;
this.g = g;
}

// Equivalent to +:
function add(f, g) {
if f=0 then g else
if g=0 then f else
if g instanceOf Add then add(add(f, g.f), g.g) else
Add(f, g)
}