Beefy Boxes and Bandwidth Generously Provided by pair Networks
laziness, impatience, and hubris
 
PerlMonks  

Re^3: Is it safe to append to the array you are iterating over

by ikegami (Pope)
on Mar 16, 2013 at 19:53 UTC ( #1023847=note: print w/replies, xml ) Need Help??


in reply to Re^2: Is it safe to append to the array you are iterating over
in thread Is it safe to append to the array you are iterating over

possibly depending on an undocumented implementation detail of my version of Perl.

You most definitely are. The loop is suppose to take a list over which to iterate, but you're relying on the observable differences between that an the actual optimised implementation. You can see this by changing foreach (@arr) to what should be equivalent foreach ((),@arr).

Either iterate over the indexes

my @arr = qw/a b c/; for (my $i=0; $i<@arr; ++$i) { my $e = $arr[$i]; push @arr, 'd' if $e eq 'a'; push @arr, 'e' if $e eq 'b'; push @arr, 'f' if $e eq 'c'; print $e; } print "\n";

Or use a queue

my @arr = qw/a b c/; while (@arr) { my $e = shift(@arr); push @arr, 'd' if $e eq 'a'; push @arr, 'e' if $e eq 'b'; push @arr, 'f' if $e eq 'c'; print $e; } print "\n";

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1023847]
help
Chatterbox?
[pryrt]: 1nickt, sprintf "%.16e", $v will always give enough precision to see 1 ULP (the smallest fractional part) of a standard 64bit Perl NV*
[pryrt]: (*: for systems where $Config{nvsize}==8 )

How do I use this? | Other CB clients
Other Users?
Others studying the Monastery: (14)
As of 2017-05-24 19:07 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?