Brethren,

while trying to "do it more than one way", I've stumbled across a weird behaviour of the ternary operator. I had this code which keeps only the recent input in history of Term::Readline: 

  if ($optimize_history) {
    # remove duplicities from history
    my @history = $term->GetHistory($file);
    my %history = map {$_ => 1} @history;
    my @new_history = ();

    for (reverse @history) {                    # in reverse order
      if ($history{"$_"}) {                     # if not remembered ye
+t
        unshift @new_history, $_;               #   remember history l
+ine
        delete $history{"$_"};                  #   and remove it
      }
    }

    $term->SetHistory(@new_history);            # set history to new l
+ist
    $term->WriteHistory($file);                 # save history
  } else {
    # only add new line to the history file
    $term->WriteHistory($file);
  }

[download]
after some refactoring (I especially didn't like the usage of so much variables/structures) I came up with something like that: 
  if ($optimize_history) {
    my @history = $term->GetHistory($file);
    my %history;

    # eliminate duplicates in history and keep only the most recent
    for(my $i=scalar(@history)-1;$i>=0;$i--) {
      $_ = $history[$i];
      !$history{$_} ? $history{$_}=1 : splice(@history,$i--,1);
    }

    $term->SetHistory(@history);            # set history to new list
  }
  $term->WriteHistory($file);               # save history

[download]
to my big surprise, when I tried to refactor the ternary operator into 
$history{$_} ? splice(@history,$i--,1) : $history{$_}=1;

[download]
I get an error message: 
Can't modify splice in scalar assignment at ./history.pl line 35, near
+ "1;"
Execution of ./history.pl aborted due to compilation errors.

[download]
Ehm...Uh? Why is that? Have I - again - been caught by some precedence issue?

Bye
 PetaMem

In reply to Ternary Operator: Condition-Negation by PetaMem

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