I have an array of strings: @array
I want to concatenate all strings beginning with array index $i to $j.
How can I do this?
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4 Answers
$newstring = join('', @array[$i..$j])
5 Comments
Rohit Banga
thanks. if $j is end of string, i am using scalar(@array)-1 for $j. is there any other way of doing that.
mob
@iamrohitbanga Yes:
$#array is a shorter way of saying scalar@array - 1
xiechao
Sorry I don't follow the "$j is end of string" part. But scalar(@array)-1 is $#array.
ephemient
The last time I said that
@array-1 == $#array, somebody pointed out that "not if $[ has been changed". Admittedly, an odd scenario that we usually don't even care to think about, most of the time...
hobbs
The point is to use the one that means what you want. Since in this case you want the last thing in
@array, you write $#array because it means the last index in @array. You don't write @array - 1 because that means "one less than the number of things in @array".my $foo = join '', @array[$i..$j];
First we generate an array slice with the values that we want, then we join them on the empty character ''.
Comments
Just enclosing a perl array in quotes is enough to concatenate it, if you're happy with spaces as the concatenation character:
@array = qw(a b c d e f g);
$concatenated = "@array[2 .. 5]";
print $concatenated;
## prints "c d e f"
or of course
$" = '-';
@array = qw(a b c d e f g);
$concatenated = "@array[2 .. 5]";
print $concatenated;
if you'd prefer "c-d-e-f".
Comments
Try this ....
use warnings ;
use strict ;
use Data::Dumper ;
my $string ;
map { $string .= $_; } @arr[$i..$j] ;
print $string ;
2 Comments
friedo
You shouldn't use
map in void context; a for loop would work just as well. But loops of any sort are unnecessary when you can just use join.
daotoad
Is void
map evil? I'd use a postfix for most places a void map can be used. Here I'd use a join. But Perl 5.8.1 and up optimize away map's return values when called it is called in void context. For more discussion of map in void context see: perlmonks.org/index.pl?node_id=296742