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Re^3: Variable number of foreach loops

by BrowserUk (Patriarch)
on Nov 27, 2013 at 18:04 UTC ( #1064678=note: print w/replies, xml ) Need Help??


in reply to Re^2: Variable number of foreach loops
in thread Variable number of foreach loops

BTW what is the third argument($i) nFor( $n-1, @_, $i ) doing here?

As the sub recurses, one of the array references is remove from the front of @_ at each level, and the current value being iterated by the for loop at that level is added to the end.

Once $n == 0, all the array references have been removed and $n has been shifted off, all that is left in @_, is the set of elements to be printed.

BTW. Here is a cleaner implementation that takes a callback to which the results sets are passed:

#! perl -slw use strict; sub nForX(&@) { my $code = shift; my $n = shift; return $code->( @_ ) unless $n; for my $i ( @{ shift() } ) { &nForX( $code, $n-1, @_, $i ); } } my @a = 1..10; my @b = 'a'..'z'; my @c = map chr, 33 .. 47; nForX { print join ' ', @_; } 3, \( @a, @b, @c );

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Re^4: Variable number of foreach loops
by abhay180 (Sexton) on Nov 28, 2013 at 05:09 UTC
    thanks a lot. yes i get it now. In the same light.....i want to call nfor() with different number of arguments...
    nfor(1,\@a_1); nfor(2,\@a_1,\@a_2); nfor(3,\@a_1,\@a_2,\@a_3);...so on nfor(N,\@a_1,\@a_2,...\@a_N).
    I have a way...but what to check if there is a much crispier way to do it.

      If you store your arrays (more specifically references to your arrays) in an array, you can say

      my @arrayOfArrays = ( \@a_1,\@a_2,...,\@a_20 ); my $n = 10; nfor( $n, @arrayOfArrays[ 0..$n-1 ] );

      Where will you get the variable number of arrays from? And how will you be storing them?


      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
        I have stored my data in N arrays. N varies from 1..20 I have a random string, that i breakdown into some N-segments. Each Segment is then a array. Now i want to run nfor() on these. So as you can see segment size is random. Hence variable number of arrays.

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