List and array of Data Types

-- Start

For the following Perl statement, $ name on the left of the equal sign is called a scalar, and "Shang Bo" on the right of the equal sign is called a String constant, it means to assign the String constant "Shang Bo" to the variable $ name.

$ Name = "Shang Bo ";

For the following Perl statement, @ names on the left of the equal sign is called an array, and the @ names on the right of the equal sign is called a list. It means that the value in the list is assigned to the array @ names.

@ Names = ("Shang Bo", "Zhang San", "Li Si ");

List

A list is a series of values enclosed in parentheses. The following example shows how to define and use the list.

#! /Usr/bin/perl ############################ define a list (); # Empty list (1, 2, 3); (1 .. 100); # contains the list of numbers 1 to 100 ('A '.. 'B'); # It can be used as a string ("Shang Bo", "Zhang San", "Li Si"); # Double quotation marks ('shang BO ', 'zhang San', 'Li si '); # single quotes QW (Shang Bo Zhang San Li Si); # Same as above (single quotes), QW indicates quoted by whitespaceqw/Shang Bo Zhang San Li Si /; # QW delimiters can be any punctuation ############################## Use List ($ name1, $ name2, $ name3) = ("Shang Bo", "Zhang San", "Li Si"); # assign values in the list to three scalar values ($ name1, $ name2, $ name3, $ name4) = ("Shang Bo", "Zhang San", "Li Si"); # the value in $ name4 is UNDEF ($ name1, $ name2) = ("Shang Bo", "Zhang San", "Li Si"); # Li Si will be ignored ($ name1, UNDEF, $ name2) = ("Shang Bo", "Zhang San ", "Li Si"); # Zhang San will be ignored ($ name1, $ name2) = ($ name2, $ name1); # the value of $ name = ("Shang Bo ", "Zhang San", "Li Si"); # the value in $ name is Li Si, And the rightmost value is @ names = ("Shang Bo", "Zhang San", "Li Si "); # assign the values in the list to an array

Array

#! /Usr/bin/perl ################################ define an array @ names; @ names = (); # Same as above @ student_names = ("Xiao Wang", "Xiao Li"); @ names = ("Xiao Shang", @ student_names); # at this time, the array @ names will contain "Xiao Shang", "Xiao Wang", "Xiao Li" @ names = @ student_names; # copy an array ############################### access an array @ names = QW (Xiao Shang Xiao Wang Xiao Li ); $ name = $ Names [0]; # retrieve the element whose subscript is 0. Note that $ Names [0] is used here. not @ Names [0] $ name = $ Names [-1]; # extract the last element of the array. Perl supports negative subscript, for example, $ Names [-2]. $ Names [-3] and so on $ Names [19] = ""; # The array will automatically grow to 20 elements, UNDEF is not defined ($ name1, $ name2, $ name3) = @ names; # assign the values in the array to the three flags on the left $ last_index =$ # names; # subscript of the last element of the array names $ # names + = 1; # change the length of the array names @ names = QW (Xiao Shang Xiao Wang Xiao Li Xiao Zhao ); @ names_part = @ Names [2, 3]; # @ the value in the names_part array is Xiao Li, Xiao Zhao @ names_part = @ Names [1 .. 3]; # @ names_part the value in the array is: Xiao Wang, Xiao Li, Xiao Zhao @ Names [2, 3] = ("s", "s"); # @ names the value in the array is: xiao Shang, Xiao Wang, da S, Xiao s @ Names [] = @ Names []; # Exchanging array elements @ Names [] = @ Names []; # exchange array elements ################################# print an array @ names = QW (Xiao Shang Xiao Wang Xiao Li ); print @ names; # output: Xiao Shang Xiao Wang Xiao Li, note that there are no spaces. Print "@ names"; # output: Xiao Shang Xiao Li print "wave0409 \ @ 163.com "; # note the escape @ When printing the email; otherwise, it will be considered as an array print "I am $ Names [0]"; ############################### iterative array $ name = "Xiao Zhao"; @ names = QW (Xiao Shang Xiao Wang Xiao Li); foreach $ name (@ names) {$ name = "hello ". $ name; # change the value of $ name and the value in the array.} Print $ name; # After the loop ends, the value of $ name will be restored to the value at the beginning of the Loop: xiao Zhao ################################ functions for Array Operations @ names = QW (Xiao Shang Xiao Wang Xiao Li ); $ name = POP (@ names); # The pop function is used to delete and return the last element in the array (Xiao Li is deleted) Push (@ names, 'xiao li '); # The push function is used to add one or more elements to the end of the array (Xiao Li is added to the end of the array) Push (@ names, @ student_names ); # Add the array @ student_names to @ names = QW (Xiao Shang Xiao Wang Xiao Li); $ name = shift (@ names ); # The shift function is used to delete and return the first element in the array (xiaoshang is deleted) unshift (@ names, 'xiaoshang '); # The unshift function is used to add one or more elements to the array header (the small element is still added to the array header) unshift (@ names, @ student_names ); # Add the array @ student_names to @ names = QW (Xiao Shang Xiao Wang Xiao Li); $ name = join ("-", @ names ); # concatenate an array element into a string: Xiao Shang-Xiao Wang-Xiao Li @ names = Split (/-/, $ name); # divide the string into an array: ("Xiao Shang", "Xiao Wang ", "Xiao Li") @ names = Split (/-/, $ name, 2); # split the string into an array and split it into two elements: ("Xiao Shang ", "Xiao Wang-Xiao Li") @ names = QW (Xiao Shang Xiao Wang Xiao Li); @ names = reverse (@ names); # reverse array: Xiao Li Xiao Wang Xiao Shang @ strings = (1, 2, 3, 10, 10, 12); @ stringsort = sort (@ strings); # Sort arrays by default (letters) @ numbersort = sort {$ A <=> $ B} (@ strings ); # custom method (number) sorting array @ numbersort = sort {"\ L $ A" CMP "\ L $ B"} (@ strings ); # custom (case-insensitive) sorting array @ names = QW (Xiao Shang Xiao Wang Xiao Li); @ names2 = QW (Small S); @ names_new = splice (@ names, 2, 0, @ names2); # insert and replace @ names, skip two elements, and replace 0 with @ names2 (equivalent to insert ): xiao Shang Xiaowang xiaos das Xiao Li @ names_new = splice (@ names, 2, 1, @ names2); # Skip two elements and replace one element with @ names2: xiao Shang Xiaowang xiaos das @ names = QW (Zhang San Li Si Wang Wu); @ result = grep (/^ Zhang/, @ names); # search for the name of the person surnamed Zhang @ numbers = (1, 2, 3); @ result = map ($ _ + 1, @ numbers); # Add 1 to each element of the array

Two-dimensional array

#! /Usr/bin/perl # defines a two-dimensional array, which is usually used to store tables $ users = [["Zhang San", 20, "Inner Mongolia"], ["Li Si", 21, "Liaoning"], ["Wang Wu", 22, "Beijing"]; # define a table with three rows and three columns # access the two-dimensional array print "@ {$ users-> [0]} \ n "; # print the first line print "@ {$ users-> [0]} [0] \ n "; # Print print the first column of the First row "$ users-> [0] [0] \ n "; # print the first column of the First row # iterate the two-dimensional array foreach $ row (@ $ users) {($ name, $ age, $ adress) =@$ row; print "$ name, $ age, $ adress \ n ";}

Scalar context and list Context

When arrays are used in different scenarios, different behaviors are displayed. For example, assigning an array to another array and assigning a scalar produce different results, as shown below.

#! /Usr/bin/perl ################################ scalar context and list context @ names = QW (Xiao Shang Xiao Wang Xiao Li ); @ names2 = @ names; # copy an array $ length = @ names; # Return the length of the array ($ name) = @ names; # Return the first element of the array: small Shang print "@ names"; # print the array print scalar @ names; # print the length of the array. The scalar function is used to forcibly specify the scalar context.

-- For more information, see Perl.

--Shengming: reprinted, please indicate the source
-- Last updated on 2012-06-24
-- Written by shangbo on 2012-06-21
-- End