Do unique work for each element of Array

Question

I create a txt file that have 3 element and i wrote this code :

my $in_file1 = 'file.txt';
open DAG,$in_file1;
my @shell=<DAG>;
close DAG;
chomp(@shell);
foreach my $shell(@shell){
 # and etc code

and i want if the number of element is 0 do something and if 1 do other thing and if 2 ... . for example

if (@shell[0]) print "hi"; if(@shell[1]) print "bye" if(@...

what am i going to do ? what is the best and simplest way for doing this ? Thanks .

Joel Berger · Accepted Answer · 2012-02-20 01:31:29Z

2

One of the best ways to do work based on a value is a hash/redirect table, especially if you need to do that sort of work more than once in a program. This involves creating a hash whose keys are the selector values, and values are references to subroutine doing work.

In your case, you are doing based on # of words, so a lookup array is a good way to go:

sub bye { print "bye"; }
my @actions = (
    sub {  },            # do nothing for 0. Using anonymous sub
    sub { print "hi" },  # print "hi" for 1
    \&bye,               # for 2 - illustrate how to use reference to existing sub
);
use File::Slurp; # To read the file
my @lines = read_file("my_file");
for (my $index = 0; $index < @lines; $index++) {
     &{ $actions[$index] }($lines[$index]); 
     # Call the sub stored in an array in correct place
     # Pass it the line value as argument if needed.
}

edited Feb 20, 2012 at 1:31

Joel Berger

20.3k5 gold badges52 silver badges106 bronze badges

answered Feb 19, 2012 at 22:12

DVK

130k33 gold badges219 silver badges337 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

user1212132 Over a year ago

i think its hardest section of programming , Thanks DVK

DVK Over a year ago

@user1212132 - not sure what you mean by hardest section. Also, on StackOverflow, it's considered a good form to accept (by clicking on a check mark next to the answer) an answer if it was helpful as a form of thanks :)

user1212132 Over a year ago

do u know what is the reason of this error : Not enough arguments for index at line 10 near "index]"

Joel Berger Over a year ago

DVK forgot the $ and rather than calling the $index variable, invoked the index function, which isn't what he meant. Fixed now.

Collectives™ on Stack Overflow

Do unique work for each element of Array

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related