Re^2: Trying to construct all possible strings from 4 bases [ATCG]

Hi Taumaril,
Thanks so much for answering me.

Using recursive along with map is way tooooo.. high for me.
Would you mind explain it with "for" loop instead?

As I don't have a strong background algorithmic way of thinking,
I would like to understand recursion in more basic way.
I hope this is not too much to ask ;-)

Regards,
Edward

Comment on Re^2: Trying to construct all possible strings from 4 bases [ATCG]

Replies are listed 'Best First'.
Re^3: Trying to construct all possible strings from 4 bases [ATCG] by Taulmarill (Deacon) on Feb 21, 2005 at 12:40 UTC
hi, it's not too mutch to ask. in fact i'm relay glad to explain some code, 'cause it shows, that you are willing to learn. so here it comes: ### my recursive subroutine ########################### sub enum { ### return the list of elements (aka nucleotides) if this is the l +ast ### recursion. ### also note that --$_[0] decrements the counter _before_ it is t +ested ################################################################## +##### return @{$_[1]} unless --$_[0]; ### define a variable which holds my return values ################################################## my @return; ### iterate over the return values of the next recursion ######################################################## for ( enum( $_[0], $_[1] ) ){ my $nuc = $_; ### iterate over all nucleotides ################################ for ( @{$_[1]} ) { push @return, $nuc . $_; } } ### return the list so far to the prior recursion ################################################# return @return; } [download] if you have problems to understand how it works, try to think about what happens, when `$_[0] = 1` then think about what happens, when `$_[0] = 2` and then you should get it. if you don't understand this at all, it could be because my english is not even close to perfect. so maybe i just didn't explain it correct, which means "don't hesitate to ask questions" :-)	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^3: Trying to construct all possible strings from 4 bases [ATCG]
by Taulmarill (Deacon) on Feb 21, 2005 at 12:40 UTC

### my recursive subroutine
###########################
sub enum {

    ### return the list of elements (aka nucleotides) if this is the l
+ast
    ### recursion.
    ### also note that --$_[0] decrements the counter _before_ it is t
+ested
    ##################################################################
+#####
    return @{$_[1]} unless --$_[0];

    ### define a variable which holds my return values
    ##################################################
    my @return;

    ### iterate over the return values of the next recursion
    ########################################################
    for ( enum( $_[0], $_[1] ) ){
        my $nuc = $_;

        ### iterate over all nucleotides
        ################################
        for ( @{$_[1]} ) {
            push @return, $nuc . $_;
        }
    }

    ### return the list so far to the prior recursion
    #################################################
    return @return;
}
[download]

$_[0] = 1

$_[0] = 2

[reply]
[d/l]
[select]