A summary of the Perl Language Primer-3rd chapter-List and array

1-list list refers to an ordered collection of titles, while array is a variable that stores a list.

More precisely, lists refer to data and arrays refer to variables.

 

Accessing elements in an array

$ fred [0] = "yabba";
$ fred [1] = "dabba";
$ fred [2] = "doo";

$ number = 2.71111;
print $ fred [$ number-1]; #dabba If the subscript is not an integer, the decimal will be truncated.
print $ fred [145] #If no subscript exists, return undef
 

Special array index to get the last element

$ rocks [0] = "one";
$ rock [99] = ‘last’;
print $ rock [$ # rock]; #last
print $ rock [-1]; #last
List direct

(1,2,3) (1,2,3,) ("friend", 11) () (1..100)
(1.7..5.7) (5..1) empty list (0,2..6,10,12)
("fred", "barrbey" m "wilma")
qw abbreviation

qw (fred barrbey wilma)

qw allows the use of any punctuation as a delimiter.

qw / fred barney betty / # can use backslash \ escape definition

 

List assignment

($ fred, $ barney, $ dino) = (‘a’, ‘b’, ‘c’);
print $ barney; #result is b

($ a, $ b) = ($ b, $ a); # a, b exchange of two variable values
Array variable assignment and shorthand

($ rocks [0], $ rocks [1], $ rocks [2]) = qw / a b c /;
@rocks = qw / a b c /; #shorthand for the above method
Array operations

@a = qw / a b /;
@b = (@ a, "c", ‘d’); # a, b, c, d
pop and push operations, the rightmost operation

@array = 5..8;
$ array1 = pop (@array); #will remove the last element 8 from the array and return 8
push @array, 100; #Add 100 backward
shift and unshift operators, which operate on the far left

@array = qw # a b c d #;
$ m = shift (@array); # @ arrayvalues are (b, c, d)
unshift (@array, 100); #Add 100 forward (that is, (100, b, c, d)
 

Perl language introduction-chapter 3-lists and arrays