Go rant

[Daniel de Kok]

On 2009-12-19 21:04:32 +0100, Andrei Alexandrescu 
<SeeWebsiteForEmail at erdani.org> said:
> "This code is shown for its elegance rather than its efficiency. Using 
> ++ in this way is not generally considered good programming practice."
> 
> So if the code is inefficient and in poor programming practice, how in 
> this blessed world could it count as elegant?

Well, it is elegant in that it is very readable, and as such provides 
educational value. There are very many examples in programming text 
books that may not be efficient, but do show the solution to a problem 
elegantly.

E.g. consider list reversal in a recursive function or predicate. It is 
easy to see that to reverse a list, you append the head to the reversed 
tail. E.g.:

reverse([],[]).
reverse([H|T],R) :-
  reverse(T,RT),
  append(RT,[H],R).

Of course, this is very inefficient, since the program is doing (slow) 
appends all the time, and is not tail-recursive. You can do it a lot 
faster with an accumulator, but it makes the solution also less 
understandable, and not something you'd want to present 
students/readers immediately:

reverse(List,Reverse) :-
  reverse_aux(List,Reverse,[]).

reverse_aux([],List,List).
reverse_aux([H|T],List,List0) :-
  reverse_aux(T,List,[H|List0]).

> I have gathered a fair amount of samples of involuntary humor from that 
> book. I wouldn't want to go on about that because it could too easily 
> be interpreted as poor taste competitiveness. Let me say I don't think 
> the book is well written.

It seems that currently the time to market is much more important than 
to provide good material, although I cannot comment on that particular 
book.

-- Daniel