I have an array with x items:
my @arr= qw( mother child1 child2 child3);
Now i want to ietrate this array. Every Loop should append an entry:
- mother
- mother/child1
- mother/child1/child2
- mother/child1/child2/child3
How i can realize this with perl?
3 Answers
Here's a slightly more idiomatic solution.
my @arr = qw[mother child1 child2 child3];
say $_ + 1, '. ', join ('/', @arr[0 .. $_]) for 0 .. $#arr;
Comments
Do you need the individual paths, or do you just want to join all the segments?
To do the latter you can just write
my $path = join '/', @arr;
(By the way, that's an awful identifier. The @ tells us that it's an array so the arr adds nothing. I don't know what your data represents, but perhaps @segments would be better.)
But if you need the loop, you can do this
use strict;
use warnings 'all';
use feature 'say';
my @arr= qw( mother child1 child2 child3 );
for my $i ( 0 .. $#arr ) {
my $path = join '/', @arr[0 .. $i];
say $path;
}
output
mother
mother/child1
mother/child1/child2
mother/child1/child2/child3
Note that this is essentially the same algorithm as Dave Cross shows but I have used a standard block for loop as I imagine that you will want to do something with the paths other than printing them, and I have removed the numbering as I think that was just an illustrative part of your question.
Comments
You can try with this solution:
my @arr= qw( mother child1 child2 child );
my $content;
my $i;
foreach (@arr){
$content .= '/' if ($content);
$content .= $_;
print "$i.$content\n";
$i++;
}
The result as you expect.
output
.mother
1.mother/child1
2.mother/child1/child2
3.mother/child1/child2/child3
Update
That should have been
use strict;
use warnings 'all';
my @arr= qw( mother child1 child2 child3 );
my $content;
my $i = 1;
foreach ( @arr ) {
$content .= '/' if $content;
$content .= $_;
print "$i.$content\n";
++$i;
}
output
1.mother
2.mother/child1
3.mother/child1/child2
4.mother/child1/child2/child3
4 Comments
Borodin
I doubt if the OP requires the numbers printing before each path. In any case,
$content .= '/' if ($i>1) is better written as $content .= '/' if $content, so the $i variable is unnecessary.Borodin
What you've written is very compact. Perl will ignore whitespace between tokens, so you should make the most of that to lay out your program so that it is readable. Also, please test your code before you post it. Look at the output from your (revised) code. If you had
use strict and use warnings 'all' in place as you should have then you would have seen the warning message Use of uninitialized value $i in concatenation (.) or stringBorodin
Please don't edit your posts so the earlier contributions make no sense.
Ngoan Tran
@Borodin: I corrected it, I'm new to stackoverflow and very appreciate your prompt.