wow.. vey good point.. thanks Laurent_R.

The central point, as many times, is a correct understanding of words and semantic they cover.
This can be useful for the OP and for other as me that have missed this difference (from wikipedia):

Recursion in computer science is a method where the solution to a problem depends on solutions to smaller instances of the same problem

Iteration is the repetition of a block of statements within a computer program

That said obviously the tachyon solution falls in the iterative category..

#excert from tachyon's code at http://www.perlmonks.org/?node_id=15785
+1
my @dirs  = ($root);

for my $path (@dirs){
    opendir ( DIR, $path ) or next;   # skip dirs we can't read
    while (my $file = readdir DIR) {
      next if $file eq '.' or $file eq '..'; # skip dot files
           if ( -d $path.$file ) {
            push @dirs, $path.$file.'/';     # add dir to list
        } 
    }
    closedir DIR;
}
[download]

but..
..the logic of the snippet IS recursive in the way it populates @dirs: in fact it iterates over a list updated dynamically while processing the iteration itself. It produes a directory tree, or well a list of different depth objects. Also here the problem is divided in small pieces to process. But in the opposite way: @dirs starts populated by the root node only and while it is processed the stack @dirs itself it is updated: the way @dirs is populated by push seems recursive, in a broad sense.

In other words, as wikipedia tell us some line below:

Recursion and iteration are equally expressive: recursion can be replaced by iteration with an explicit stack, while iteration can be replaced with tail recursion.


Hth
L*

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.