From: Robert Klemme <bob.news@...>
Date: 2003-05-12T18:40:06+09:00
Subject: Re: efficiency advice needed


"Mauricio Fern�ndez" <batsman.geo@yahoo.com> schrieb im Newsbeitrag
news:20030512092410.GA22416@student.ei.uni-stuttgart.de...
> > > width = height = ARGV[0].to_i
> > > data = String.new(" " * 4*width*height)
> >
> > You don't need the String.new here - this only creates a superfluous
copy.
> > Better do
> >
> > data = " " * (4*width*height)
>
> Stupid of me, yes. I was thinking C there (init buffer with given capa.
:-)

Don't worry, such things happen to all of us all the time. :-)

> > If you want to append to a string, using "<<" or "concat" is better
than
> > "+=" since "+=" creates a new instance every time.  You can verify it
like
> > this:
>
> That was the point of my post (see first example), but in this case you
> can get more speed by initializing the string to the given size and then
> replacing characters inside with #[]=; this way you don't waste time
> realloc()ating the string buffer (which would happen if you use
> String#<<).

That's true.  I just wanted to point out that "<<" is better for cases
where you can't do preallocation.  Maybe I should've read the beginning of
your post more carefully and written my point more clearly.

Regards

    robert