PERL Beginners - Delete an element in an array

Author

Delete an element in an array

Oliver Fuchs

2005-02-21, 8:56 pm

Hi,

I want to save names from <STDIN> to an array.
Afterwards I want to delete a single name in the array received again from
<STDIN>.

This is what I have:

#!/usr/bin/perl

use warnings;

print "Some names please: \n";
@names = <STDIN>;
print "Delete one name? \n";
$deleted = <STDIN>;
foreach $item (@names) {
unless ($item eq $deleted){
push (@aonly, $item);
}
};
print "Your names:\n", @aonly, "\n";

My question is how can I delete an element of the array directly (something
like
pop (@names, $item);
).
Is there a chance to delete it without using the index?

Oliver
--
.... don't touch the bang bang fruit

Wagner, David --- Senior Programmer Analyst --- WG

2005-02-21, 8:56 pm

Oliver Fuchs wrote:
> Hi,
>=20
> I want to save names from <STDIN> to an array.
> Afterwards I want to delete a single name in the array received again
> from <STDIN>.
>=20
> This is what I have:
>=20
> #!/usr/bin/perl
>=20
> use warnings;
>=20
> print "Some names please: \n";
> @names =3D <STDIN>;
> print "Delete one name? \n";
> $deleted =3D <STDIN>;
> foreach $item (@names) {
> unless ($item eq $deleted){
> push (@aonly, $item);
> }
> };
> print "Your names:\n", @aonly, "\n";
>=20
>=20
> My question is how can I delete an element of the array directly
> (something like
> pop (@names, $item);
> ).
> Is there a chance to delete it without using the index?
>=20
> Oliver
> --
> ... don't touch the bang bang fruit

You would use splice to remove an item. But if I was going to do this, th=
en I would use a hash and then delete the item and not do the searching thr=
ough the array. If you only have 5 items, okay, but 10000 then you have to =
search at least 5000 entires ( on avg ) to get your item. But if name is th=
e key into the hash, then one action to delete the name.

Wags ;)

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Bob Showalter

2005-02-22, 8:55 am

Oliver Fuchs wrote:
> Hi,
>
> I want to save names from <STDIN> to an array.
> Afterwards I want to delete a single name in the array received again
> from <STDIN>.
>
> This is what I have:
>
> #!/usr/bin/perl
>
> use warnings;

We always recommend:

use strict;

>
> print "Some names please: \n";
> @names = <STDIN>;
> print "Delete one name? \n";
> $deleted = <STDIN>;
> foreach $item (@names) {
> unless ($item eq $deleted){
> push (@aonly, $item);
> }
> };

This can be written as:

@aonly = grep $_ ne $item, @names;

or, if you just want one array:

@names = grep $_ ne $item, @names;

> print "Your names:\n", @aonly, "\n";
>
>
> My question is how can I delete an element of the array directly
> (something like
> pop (@names, $item);
> ).
> Is there a chance to delete it without using the index?

No; you have to know the index, or use a hash instead of an array.

>
> Oliver
> --
> ... don't touch the bang bang fruit

Oliver Fuchs

2005-02-26, 8:55 am

On Mon, 21 Feb 2005, Wagner, David --- Senior Programmer Analyst --- WGO wrote:

> Oliver Fuchs wrote:
>
> You would use splice to remove an item. But if I was going to do this, then I would use a hash and then delete the item and not do the searching through the array. If you only have 5 items, okay, but 10000 then you have to search at least 5000 entires
( on avg ) to get your item. But if name is the key into the hash, then one action to delete the name.
>
> Wags ;)
>

Hi,
thanks for answering. So I have to use a hash ... will try it.

Thanks
Oliver
--
.... don't touch the bang bang fruit

Oliver Fuchs

2005-02-26, 8:55 am

On Mon, 21 Feb 2005, Bob Showalter wrote:

> Oliver Fuchs wrote:
>
> We always recommend:
>
> use strict;
>
>
> This can be written as:
>
> @aonly = grep $_ ne $item, @names;
>
> or, if you just want one array:
>
> @names = grep $_ ne $item, @names;
>
>
> No; you have to know the index, or use a hash instead of an array.
>

Thanks for your help. So i will try to use a hash.

Oliver

--
.... don't touch the bang bang fruit

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