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Re: How to find size of array in array?

by jbert (Priest)
on Nov 19, 2001 at 19:35 UTC ( #126279=note: print w/ replies, xml ) Need Help??


in reply to How to find size of array in array?

Good advice in the other responses. Some more words for you:

Your line of code to find the length:

$asize = @a;
works because an array evaluates to the number of elements it contains in a scalar context. Assigning to a scalar (as you do above) provides a scalar context to the right hand side (RHS). So the array is evaluated in this scalar context, giving the length, which the assignment then puts into your '$asize' variable.

Why did I bother spelling this out in a long-winded way? Because it is useful to understand what it going on. For example, I usually write the above as:

my $asize = scalar @a;
The 'scalar' keyword supplies a scalar context to its argument and gives the result of the evaluation. It is redundant in the above example (because we already have a scalar context from the assignment to the scalar).

So why do I write it like that? Because:

  • It is an explicit statement of what I am doing. I consider that more readable.
  • I can use the same syntax every place I need an array size. Look at the following:
    #!/usr/local/bin/perl -w use strict; my @array = qw( 1 2 3 4 5 ); my $asize = scalar @array; print "Array size 1 is ", $asize, "\n"; print "Array size 2 is ", @array, "\n"; print "Array size 3 is ", scalar @array, "\n";
    I *need* to use the scalar keyword here, because otherwise the 'print' command gives a list context to the array, which lists all the elements instead of giving the size.

    Since I sometimes get cut-and-paste happy, it is nice to have code which is explicit about what context it wants.

And I'll conclude this overly-pedantic missive to state that you should look into using 'use strict' and '#!... -w', to force you into good habits. (Heh...habits! Monks! How funny is that!? (Hrrrm...the first couple of million times were probably worth chuckling at, but thats about it))


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Re^2: How to find size of array in array?
by Anonymous Monk on Apr 23, 2007 at 03:43 UTC
    For getting the size of an array @array, you can just use the variable as $#array. Shashidhar Iddamsetty

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