where to look up "funny looking" perl notation (and an example)

[glwtta]

Silly question for the monks:

ok, when I have something like this: $#{$some_var[$i]} and I don't know what it does, where is a good place to look these things up? Googling isn't exactly heplful when you want to find '$#{'

Also, what does the above notation, infact, mean?

[Mr. Muskrat]

perldoc perldata would have told you that $# means 'the last index of array'. In this case, it's the last index of the array referenced by $some_var[$i].

See also: References quick reference.

[glwtta]

d'oh. guess that's a clear case of lack of RTFMing

Since we are on the subject, am I right in thinking that the 'last index' will always be one less than scalar @array? Or is there something more to it?

[Gilimanjaro]

Almost always true...

If it wasn't for the fact that you can change the base-index of perl arrays to something other then 0... But I've never seen anyone use that feature yet. The global parameter for the feature is '$['.

So use $# to get the last defined element index so you can safely add (or loop), and use scalar @array to find out how many elements there are in the array...

[Mr. Muskrat]

You are correct...

Once again, perldoc perldata to the rescue...

scalar(@whatever) == $#whatever + 1;

[sschneid]

Luckily enough, your answer can be found in the documentation that comes with perl itself! Check out perldoc perldata from the command line.

[scain]

Another place to look up "funny looking" things is perldoc perlvar, where you can find the meaning of $&, $!, and $^O.

Scott
Project coordinator of the Generic Model Organism Database Project

[pg]

1. As others already pointed out that most likely your $some_var[$i] is an array reference.
   
   However, just for completeness, I want to point out that it could also be a symblic reference. If use strict is truned off for refs, that would be also correct from a syntax point of view.
   
   However I am not a supporter of the symbolic ref usage.
   
   
2. It is worth to mention to new perl users, that $# can be used as lvalue.
   
   This is extreamly useful, when you want perl to garbage collect your big arrays.
   
   Just do

   @a = (1..1000);
   print "original array:\n";
   print join(",", @a), "\n";
   $#a = -1;
   print "after set to -1:\n";
   print join(",", @a), "\n";#You can not say for sure that your array ha
   +s already been garbage collected at this point, but at least it is no
   +w a candidator.
   

[Hofmator]

For the sake of garbage collection - if you are 'deleting' the whole array - I prefer the more readable @array = ();


-- Hofmator