Re: [phplib] PHP and recursion From: Roy Huggins (roy <email protected>)
Date: 05/31/01

Hola.

Wonderful! These are exactly the kinds of comments I was looking for. Keep 'em
coming and thanks to everyone!

Luckily, I do own the esteemed Mr. Ratschiller's book. I guess I need to give it
some more of my attention...

Regards,
Roy Huggins
roy <email protected>
http://www.royhuggins.com/employability

----- Original Message -----
From: "D. Sebastien Taggart" <dlst <email protected>>
To: <phplib <email protected>>
Sent: Thursday, May 31, 2001 3:02 PM
Subject: FW: [phplib] PHP and recursion

> >From that very book, "Web Application Development with PHP 4.0", Tobias
> Ratschiller, 0-7357-0997-1:
>
> "PHP 3.0 doesn't have proper garbage collection. When reallocating a
> variable, memory that's already been allocated is not always being reused.
> ... this might result in 'dead memory'"
>
> In other words, check your garbage collection routines, and check to make
> sure you don't have any "runaway" nodes. Since PHP works with "copies" and
> not pointers, the whole concept of recursion can get tricky if you're not
> really careful... THAT'S what Mr. Ratschiller was saying in this great book,
> NOT that one shouldn't use recursion. (In fact, it's impossible to handle
> tree structures without using recursion).
>
> And BTW, see pg. 53 of the very same book. They go over a simple example of
> exactly what it sounds like you're trying to implement.
>
> -Sebastien
>
>
> -----Original Message-----
> From: Paul Smith [mailto:paul <email protected>]
> Sent: Thursday, May 31, 2001 9:16 AM
> To: phplib <email protected>
> Subject: Re: [phplib] PHP and recursion
>
>
> Yikes, that is dubious advice. Recursion is one of the things that
> makes programming so great! It is a powerful concept, *not* some obscure
> or obtuse feature. Casually dismissing it is akin to blowing off, say,
> object-orientation, or abstraction. I highly encourage you to explore the
> application of recursion further, not less, because it can dramatically
> reduce complexity and reveal solutions that are otherwise unattainable.
>
>
> On Thu, May 31, 2001 at 03:30:41PM +0100, James Johnson wrote:
> > Roy
> >
> > I seem to recall Tobias Ratschiller's book,Web Application
> > Development with PHP 4.0 talks about using recursion.
> > I think he says it can be useful under certain unusual
> > circumstances, but to avoid it generally.
> >
> > James
> >
> >
> > At 09:07 AM 5/31/01 -0500, Roy Huggins wrote:
> > >Hola.
> > >
> > >My question is not related to PHPLib specifically, for which I apologize.
> But
> > >the members of the list have oft displayed good knowledge of the
> underworkings
> > >in PHP and I'd like to get some insight into something I've run into
> recently.
> > >
> > >I recently built a pair of classes whose purpose is to create a tree of
> > >TreeNode
> > >objects in which each node has one parent, many children and an array of
> > >arbitrary data. Performing operations on these trees uses a lot of
> > >recursion, of
> > >course. Upon testing one function that traverses the tree, creating an
> > >array of
> > >path illustration strings through the tree (i.e. $paths[0] ==
> > >"root:node1:node2", $paths[1] == "root:node1:node4:node7"), PHP quit
> while
> > >complaigning about using too much memory. My script was using a whopping
> 8
> > >megs!
> > >
> > >I examined my code to see if I was doing something stupid to fill up the
> > >RAM and
> > >didn't find anything (which, of course, doesn't mean it isn't there. :)
> But I
> > >wanted to get some more info on how PHP deals with recursion and whether
> > >or not
> > >people have any comments/caveats to express on the issue. I've been
> spoiled by
> > >Scheme and find that recursion is wonderful at times. I'd like to know if
> it's
> > >really a good idea to use it that much in PHP.
> > >
> > >Thanks in advance!
> > >
> > >Regards,
> > >Roy Huggins
> > >roy <email protected>
> > >http://www.royhuggins.com/employability
> > >
> > >
> > >
> > >
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> > Managing Director
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> >
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> --
> Paul Smith <paul <email protected>>
> InfoTech Designer
> Center for Neighborhood Technology
> Chicago, Illinois USA
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