I've never seen this before - $#a = 4

emilford has asked for the wisdom of the Perl Monks concerning the following question:

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Re: I've never seen this before - $#a = 4 - ?? by robobunny (Friar) on Jun 26, 2002 at 18:01 UTC
$#a is the last index of the array @a. setting it to something lower than what it already is will truncate the array. `@a = (0..10); print join(" ", @a), "\n"; $#a = 5; print join(" ", @a), "\n";` [download] 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5	[reply] [d/l]
Re: I've never seen this before - $#a = 4 - ?? by dws (Chancellor) on Jun 26, 2002 at 18:03 UTC
Assigning to `$#a` is a seldom-used way of truncating the array `@a`. `$#a = 4;` arranges for the final index of `@a` to be 4. Hence, `@a` will hold 5 elements. I find that using a slice makes the code more readable. `@a = @a[0..4];`	[reply] [d/l] [select]
•Re: Re: I've never seen this before - $#a = 4 - ?? by merlyn (Sage) on Jun 26, 2002 at 18:14 UTC
I find that using a slice makes the code more readable. But not as efficient as: `splice @a, 5;` [download] -- Randal L. Schwartz, Perl hacker	[reply] [d/l]
Re: I've never seen this before - $#a = 4 - ?? by mfriedman (Monk) on Jun 26, 2002 at 18:08 UTC
That can be used to allocate memory for an array before filling it up. It created five elements in @a and sets them all to undef. Here's an example: `perl -MData::Dumper -e '$#foo = 4; print Dumper \@foo'` [download]	[reply] [d/l]
Re: I've never seen this before - $#a = 4 - ?? by joshua (Pilgrim) on Jun 26, 2002 at 18:03 UTC
`$#a = 4; # Sets the length of the array @a to four print scalar(@a); # Prints how many elements are in the @a array.` [download] Remeber, arrays start with 0 as the first item.	[reply] [d/l]
Re^2: I've never seen this before - $#a = 4 - ?? by Aristotle (Chancellor) on Jun 26, 2002 at 18:39 UTC
Unless of course, someone was a bad boy and played with `$[` Makeshifts last the longest.	[reply]
Re: I've never seen this before - $#a = 4 - ?? by emilford (Friar) on Jun 26, 2002 at 18:09 UTC
That was quick. Thanks for the response.	[reply]