Go rant

[retard]

Tue, 22 Dec 2009 14:51:55 -0600, Andrei Alexandrescu wrote:

> retard wrote:
>> I use the Okasaki book as my bible when talking about purely functional
>> data structures.
> 
> It's an awesome book. It's also very frank and tells things as they are,
> as opposed to others (*cough*) that patronize the reader by artificially
> making it seem so easy, it's amazing how Stoopid People missed the
> point. Un-incidentally, Okasaki does not dabble in qsort. He does
> describe mergesort - a perfectly sound and advantageous sorting methods
> for lists.
> 
> Ok, I'm itching to share another gem.
> 
> "At this point you might be wondering how it's possible to program
> without variables. How can you express something like X = X + 1 in
> <language erased to protect the guilty>? The answer is easy. Invent a
> new variable whose name hasn't been used before (say X1), and write X1 =
> X + 1".

That's a nasty limitation indeed. From my point of view imperative 
languages just pass around the global state with the value of the 
computation, and the assignment (X=X+1) shadows the previous value of X. 
In some cases this allows optimizing compilers to perform the assignment 
in-place! :o) In fact, this is exactly what happens in another pure 
functional language (name erased to protect the awesomeness):

 foo x
   # x = x + 1
     x = x * 2
     x = x - 5
   = x

vs

T foo(T)(T x) {
  x = x + 1;
  x = x * 2;
  x = x - 5;
  return x;
}