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Ah! I see what you mean. (I should have realised that, given you were advocating mapcar() (What the...?) :).

The main reason for my avoiding lexicals in a utility sub of this type is that I want to retain the aliasing nature of @_. If you look closely at the output from the second and third print statements, you'll see that they have side-effects. (Which will probably be considered as undesirable, but again, it is sometimes useful.)

Perhaps these are more palatable?

#! perl -slw use strict; use List::Util qw[ min ]; local $, = ' | '; use constant { CODEBLOCK => 0, ARRAY_ONE => 1, ARRAY_TWO => 2, }; sub zip (&\@\@) { map { $_[CODEBLOCK]->( $_[ARRAY_ONE][ $_ ], $_[ARRAY_TWO][ $_ ] ) } 0 .. ( @{ $_[ARRAY_ONE]} < @{ $_[ARRAY_TWO] } ? $#{ $_[ARRAY_ONE] } : $#{ $_[ARRAY_TWO] } ); } my @x = 'a' .. 'z'; my @n = 1 .. 10; print zip{ "@_" } @x, @n; print zip{ $_[ 0 ] .= $_[ 1 ] } @x, @n; print zip{ $_[ 0 ] .= $_[ 1 ] } @x, @n; sub zipn (&\@\@;\@\@\@\@\@\@\@\@\@\@\@\@\@\@\@\@\@\@) { map { my $i = $_; $_[CODEBLOCK]->( map{ $_[ $_ ][ $i ] } 1 .. $#_ ) } 0 .. min map{ $#{ $_ } } @_[ 1 .. $#_ ]; } my @a = split'','ARC'; my @b = 1 .. 3; my @c = split'','ADP'; my @d = ( 1, 2, 0 ); print "\n---\n"; print for zipn{ join '', @_ } @a, @b, @c, @d; __END__ [17:21:15.53] P:\test>406231 a 1 | b 2 | c 3 | d 4 | e 5 | f 6 | g 7 | h 8 | i 9 | j 10 a1 | b2 | c3 | d4 | e5 | f6 | g7 | h8 | i9 | j10 a11 | b22 | c33 | d44 | e55 | f66 | g77 | h88 | i99 | j1010 --- A1A1 R2D2 C3P0

Now, if anyone can tell me how to make zipn truely generic in the number of arrays it can deal with I'd be very interested. 20 is probably more than enough for any purpose I am likely to encounter, but I hate arbitrary limits.

Also, if anyone can see how to retain the alias status of the parameters to zipn, that would be really cool.


Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon

In reply to Re^5: Gratuitous use of Perl Prototypes by BrowserUk
in thread Gratuitous use of Perl Prototypes by grantm

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