From: Markus <markus@...>
Date: 2004-10-13T01:28:23+09:00
Subject: Re: Ruby Directions (was Re: quality of error messages)

On Tue, 2004-10-12 at 06:36, Alexander Kellett wrote:
> On Tue, Oct 12, 2004 at 10:23:12PM +0900, Gavin Sinclair wrote:
> > Perhaps there are some uses of strings for which immutability makes
> > performance sense, and some uses for which it doesn't.  I couldn't be
> > bothered thinking about it :)
> 
> i can't imagine many cases where its less performant in fact.
> immutable strings with cow are obviously far faster for copying
> than mutable strings and as with most systems its the copy / 
> construction of strings rather than the iteration that takes 
> the time i'd say its logical that they should be immutable.
> (if you look at the most common c/c++ programs (excepting apps 
>  using trolltech's qt which solves the problem fairly neatly) 
>  you'll see that strcpy and memory allocation take up a huge 
>  chunk of execution time)
> 
> still... for coding, i love slice! / gsub! etc. they are 
> amazingly useful constructs. i can't imagine living without
> them :)

     The odd thing is, all you are generally getting with them is a bit
of syntactic sugar.  Consider the relationship between:

    s = gsub(p,v)
    s.gsub!(p,v)

    i = i + k
    i += k

Unless you have lent a friend a reference to s and are using it to send
secret messages, you aren't really depending on the mutability of
strings so much as the modifability of variables.

-- Markus