How to have Perl repeat the entire sentence with each variable

Question

Consider:

#! /usr/bin/perl
@no = (1 .. 20000);
foreach(@no) {
    print "<div id=\"world@no\" onclick=\"javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()\">&nbsp;</div>\n";
}

This is my Perl script, but how do I get it to rewrite the sentence with a new variable each time?

I.e., how do I get it to output the following?

<div id="world1" onclick="javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()">&nbsp;</div>
.
.
.
<div id="world20000" onclick="javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()">&nbsp;</div>

Note: Not to be confused with *[How can I repeat a string N times in Perl?](https://stackoverflow.com/questions/277485/)* (the search engines can't tell the difference). — Peter Mortensen, Aug 23 '23 at 19:53

score 3 · Answer 1 · answered Jul 21 '11 at 09:34

Your main problem is interpolating the whole array into your string instead of the loop variable ($_ in your case since you didn't specify one, but I prefer to give it a name).

You can avoid needing to escape the "s by using a different delimiter for your string:

use strict;
use warnings;
for my $world_no (1..20000) {
    print qq!<div id="world$world_no" onclick="showDiv_postscreen(); hideDiv_welcomebuttons()">&nbsp;</div>\n!;
}

Also, the "javascript:" is only necessary for things like <a href="..."> where a url is expected and you want to supply javascript code instead. It's not needed for onclick, certainly not twice.

At least one answer makes like easier. We need those backslashes so don't waste them. :) — brian d foy, Jul 21 '11 at 19:24

score 1 · Answer 2 · answered Jul 21 '11 at 09:29

1

#!/usr/bin/perl 
my @no = (1 .. 20000); 
foreach my $i (@no) { 
    print "<div id=\"world$i\" onclick=\"javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()\">&nbsp;</div>\n"; 
}

answered Jul 21 '11 at 09:29

Alexandr Ciornii

7,346
1
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Why not just use: `foreach my $i (1 .. 20_000)`, otherwise you are loosing memory to prelocate the array size – Dimitar Petrov Jul 21 '11 at 10:28
@Dimi Or `for (my $i = 1; $i <= 20_000; $i++)` to avoid loading any memory. ;) Or a while loop, like in my answer. – TLP Jul 21 '11 at 12:27
This is the example, in real program array may be created some other way, not every number. – Alexandr Ciornii Jul 21 '11 at 12:35
@TLP: That's also a solution, however I just dont like that syntax ;) Alexandr: My point was that you don't need to create the array at all, because you allocate memory for 20_000 elements. – Dimitar Petrov Jul 21 '11 at 12:39
TLP: for(;;) doesn't save any memory over for(..) – ysth Jul 21 '11 at 19:30
@ysth You mean that it still extrapolates into a list before the loop begins? – TLP Jul 22 '11 at 12:29
@ysth You may wish to have a chat with Chas. He seems to think that it does. Do you mean to say that `for (...)` does not expand its arguments into a list before the loop begins? – TLP Jul 22 '11 at 20:56
@TLP: specifically for over a range operator – ysth Jul 22 '11 at 21:01

score 1 · Answer 3 · answered Jul 21 '11 at 09:32

1

#! /usr/bin/perl
@no = (1 .. 20);
foreach $x (@no) {
print "<div id=\"world$x\" onclick=\"javascript:showDiv_postscreen()\;javascript:hideDiv_welcomebuttons()\">&nbsp;</div>\n";
}

answered Jul 21 '11 at 09:32

cppcoder

22,227
6
56
81

score 0 · Accepted Answer · answered Jul 21 '11 at 09:28

The @ in the print statement is confusing the interpreter. Also, it isn't what you want, since print "@no" would print out the same thing as join(' ',@no). Instead, you want to interpolate each element of @no into the string that's printed out:

#! /usr/bin/perl 
use strict;
use warnings; #Always use these!
my @no = (1 .. 20000); 
foreach(@no) { 
print "<div id=\"world" . $_ . "\" onclick=\"javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()\">&nbsp;</div>\n"; 
}

score 0 · Answer 5 · answered Jul 21 '11 at 10:12

I would consider using a variable to count, instead of defining a range. It may feel less intuitive, but it is not.

Also, instead of escaping the double quotes (\"), you can use qq(), which is equivalent.

my $i = 1;
print qq(<div id="world$i" onclick="javascript:showDiv_postscreen(); javascript:hideDiv_welcomebuttons()">&nbsp;</div>\n) while ($i++ <= 20_000);

How to have Perl repeat the entire sentence with each variable

5 Answers5