1. State the Basic Difference between Array in C-Language and Array in PERL:
Arrays/List are variable length.
Array/List can be declared without length.
This length can vary even after creation.
Array/List can contain any sorts of scalars (even a combination of strings, numeric, etc.) I.e it is heterogeneous.
2. Is the below is valid or invalid ?
my @array3 = (@array1, @array2);
It merges the two array in RHS into a Single Array at LHS.
3. Pick Up The Invalid Array
my @arr = (1, 2, 3);
my @arr = ("orange", 2.7);
my @arr = ($b, 21, $c);
my @arr = ();
my @arr = (1..5);
my @arr = (1..3, 7, 11..13);
my @arr = ($b .. $c);
my @arr = ("apple", "orange", "jackfruit", "grapes");
my @arr = qw(apple orange jackfruit grapes);
Run the following code snippet in your machine. See the video down below this article for explanation.
4. State the difference between scalar(@array) and $#array
scalar(@arr) ; #gives the array length
$#arr # gives the index of the last element of array
5. Please let us know if this invalid :
$arr[-1]
$arr[-2]
Both gives the element of @arr from the backside.
6. Is @arr[2,4] is a Two Dimensional Array ?
No this is called Array Slicing.
my $arr = qw(apple orange jackfruit grape mango);
@arr[2,4] # is not a two dimensional array, it is ($a[2], $a[4]);
my @subArray1 = @arr[2,4] # actually is ("jackfruit" "mango") ;
my @subArray2 = @arr[2..4] # actually is ("jackfruit" "grape" "mango");
7. How Can you Sort an Array Numerical Ascending or Descending order ?
@sorted = sort { $a <=> $b } @unsorted; # sorts integer/real (ascending Order)
@sorted = sort { $b <=> $a } @unsorted; # sorts integer/real (descending Order)
# N.B = Here $a & $b are PERL reserved Variable , no need to declare them
8. Tell Me What are the LHS values in each below case :
my ($first, $second) = @array;
my ($first, @rest) = @array;
my (@copy, $dummy) = @array;
Ans :
my ($first, $second) = @array;
$first and $second are assigned the first and second elements of @array,
my ($first, @rest) = @array;
$first is assigned the first element of @array, and @rest is assigned everything else.
my (@copy, $dummy) = @array;
In this case $dummy is not assigned.
Arrays are variable-length, so @copy has no reason to stop.
Hence $dummy ends up with undef since @copy “eats up” the entire available array.
9. How you can access Key/Value Pair at once i.e. using a single command ?
while (($key,$value) = each(%hash)) {
print “Key = $key has Value = $value \n”;
}
10. How you can covert Array into Hash and vise versa ?
my @arr = %hash; # converts a hash into a array
my %newHash = @arr; # converts array back to a hash
Provided in each case the elements in the array are even number.
11. For an unknown Reference How you can check what is the corresponding data type ?
We have to use a perl inbuilt function called “ref “ in the following way :
print "\n ref($scalarref)";
print "\n ref($arrayref)";
print "\n ref($hashref)";
print "\n ref($constref)";
12. How do you De-Reference a scalar/array/hash Reference Variable ?
my $dRef = $$scalarref; #De-Reference a Scalar
my @arr = @$arrayref; #De-Reference a Array
my %hash = %$hashRef; #De-Reference a Hash
13. How Do you De-Reference an Anonymous Array Elements?
# Accessing A Value
print "$ArrayRef->[0]";
print "$HashRef->{"KEY"}";
# Assigning A Value
$ArrayRef->[0] = "January"; # Array element
$HashRef->{"KEY"} = "VALUE"; # Hash element
14. Without using any LOOP how can you print a complete data-structure in the STDOUT ?
use Data::Dumper;
print Dumper($refDataStructure);
15. What is Globbing ?
Definition: The expansion of filename argument patterns into a list of matching filenames.
my @files = </home/docs/*.c>; # grabs list of files ending in .c
my @files = glob("/home/docs/*.c"); # same thing using glob operator
while (my $file = <abc*.html>) {
# output each .html file starting with abc
print "File: $file \n";
}
foreach my $file (<abc*.html>) {
# output each .html file starting with abc
print "File: $file \n";
}
For detailed Explanation please watch the below video :
