Re^6: loop surprise

Maybe it is a code smell...

But what I was trying to do is to find the smallest number in a certain range satisfying some condition and then go on using that found value.

Doing it like

my $i;

for $i (1..10) {
  last if &condition($i);
}

&do_more_stuff_with_the_value_found($i);
[download]

Looked (at the time) to be a straightforward solution and I was suprised that it did not work.

This is just for explaining where this comes from (I am not a really good programmer I am afraid...)

And even accepting that this is not the way to do it (there are of course many other ways), it is neverthless surprising that this actually does work:

my $i;

for ($i=1; $i<=10; $i) {
  last if &condition($i);
}

&do_more_stuff_with_the_value_found($i);
[download]

This is to my eyes at least an inconsistency (and thus a wart). But whatever, this is how it was, is and will be...

Comment on Re^6: loop surprise Select or Download Code

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Re^7: loop surprise by Your Mother (Archbishop) on Apr 04, 2018 at 00:38 UTC
That use case is completely sensible. Your original was a string overwritten with a count and reminded me of the awful code I've had to deal with over the years where there is one `$i` or `$output` and friends shared around huge scopes or even more than one script, concatted or overwritten willy nilly. Your use case in a small scope seems totally kosher though it's outside my style or sensibility.	[reply] [d/l] [select]
Re^7: loop surprise by Skeeve (Parson) on Apr 04, 2018 at 10:02 UTC
I can remember that long time (say: 30 or more years) ago, I also wrote loops like that. But now that you mention it, and thinking about it, I notice always write those kind of loops like: `my $interesting_index= 'not existing'; for ($i=1; $i<=10; ++$i) { next unless &condition($i); $interesting_index= $i; last; } # spit an error if $interesting_index is still 'not existing'` [download] The reason behind this is simply that your loop might not have found a valid value. `s$$([},&%#}/&/]+}%&{});#$&&s&&$^X.($'^"%]=\&(\|?{%` `+`.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e	[reply] [d/l] [select]
Re^8: loop surprise by Marshall (Canon) on Apr 04, 2018 at 17:59 UTC
There are many variants of how to do this. My inclination might be: `my $interesting_index; my $i = 0; while (!defined($interesting_index) and $i++ <= 10) { $interesting_index = $i if condition($i); } # spit an error if $interesting_index is still 'not defined'` [download] If the purpose of the loop is to find an index, then I would try to make that fact prominent at the start of the loop. That way you don't have to read the body of the code to figure out the purpose/intent. In Perl often there are other ways to do something similar to this functionality with the various List::utils. My Perl code rarely uses any $i subscripts. update: maybe I have an "off by one" error in original post. I think it is also possible to use the C style loop: `for (my $i=1; !defined($interesting_index) and $i<=10; $i++){}` [download]	[reply] [d/l] [select]
Re^7: loop surprise by BillKSmith (Monsignor) on Apr 04, 2018 at 04:18 UTC
I have made this mistake in the past. I now usually avoid the issue by using a function such as "first_index" in List::MoreUtils. Bill	[reply]


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