Implicit split to @

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

Goodly monks - In my sort functions, I use split(//,$a) to get length of string $a, etc. I am getting a complaint from 'use strict' as follows:

Use of implicit split to @_ is deprecated at ./spiceparam.pl line 665.
Use of implicit split to @_ is deprecated at ./spiceparam.pl line 666.
[download]

Here is the offending sub (which was shorter originally):

sub by_value_length
{
    my $sa = split(//,$vartable{$a});
    my $sb = split(//,$vartable{$b});
    ($sa <=> $sb) ||
    ($vartable{$a} cmp $vartable{$b}) ||
    ($a cmp $b);
}
[download]

Can someone please explain my offense? TIA!!! :D

Comment on Implicit split to @_ Select or Download Code

Replies are listed 'Best First'.
Re: Implicit split to @_ by tlm (Prior) on Apr 14, 2005 at 16:28 UTC
Just use the `length` function: `my $sa = length( $a ); my $sb = length( $b );` [download] the lowliest monk	[reply] [d/l] [select]
Re^2: Implicit split to @_ by samizdat (Vicar) on Apr 14, 2005 at 16:39 UTC
gaak! /me {red}. Thanks, PP, Jaap, crashtest!!!	[reply]
Re: Implicit split to @_ by crashtest (Curate) on Apr 14, 2005 at 16:36 UTC
From the documentation for split: In scalar context, returns the number of fields found and splits into the @_ array. Use of split in scalar context is deprecated, however, because it clobbers your subroutine arguments. And the output I get from `use diagnostics`: `Use of implicit split to @_ is deprecated at test.pl line 7 (#1). (D deprecated) It makes a lot of work for the compiler when you clobber a subroutine's argument list, so it's better if you assign the results of a split() explicitly to an array (or list).` [download]	[reply] [d/l] [select]
Re: Implicit split to @_ by gellyfish (Monsignor) on Apr 14, 2005 at 16:47 UTC
If you want to do it like that for whatever reason you may have (rather than using `length` as others have suggested) you will need to use a temporary array: `my $sa = do { my @tmp = split //, $vartable{$a} };` [download] The `do` block is there just to reduce the scope of the temporary array - you can do away with it if you want to predeclare the array. Of course I would recommend that you do this with `length` /J\	[reply] [d/l] [select]
Re^2: Implicit split to @_ by ysth (Canon) on Apr 14, 2005 at 22:30 UTC
`my $sa = () = split //, $vartable{$a}, -1` also does the trick. (Update: added necessary -1.)	[reply] [d/l]
Re^3: Implicit split to @_ by gellyfish (Monsignor) on Apr 15, 2005 at 10:12 UTC
Er are you sure: `perl -e 'my $sa = () = split //,"foo"; print $sa'` [download] vs `perl -e 'my $sa = do {my @tmp = split //,"foo"}; print $sa'` [download] split() is outwitting us here - it sees the empty list and optimizes accordingly. /J\	[reply] [d/l] [select]
Re^4: Implicit split to @_ by Anonymous Monk on Apr 15, 2005 at 15:12 UTC
Re: Implicit split to @_ by Jaap (Curate) on Apr 14, 2005 at 16:29 UTC
I assume it is because you call `split` in scalar context. You could also use `my $sa = length($vartable{$a});`	[reply] [d/l] [select]