Chapter 3 list and array of perl Introduction

Preface

Repeat the concept of singular and plural in Perl: Scalar represents the singular, while list and array represent the plural in Perl.
Definition:
List): An ordered set of metric quantities. ------- Storage scalar
Array (array): Stores the list of variables. -------- Store Variables
The preceding two are ordered sets. Each element in the array or list has an integer as the index. The number increases from 0 and 1 is added each time.
Note:The list and array can contain any number of elements. It can have at least no elements and can fill up all available memory. ---Adhere to the perl principle of "removing unnecessary restrictions".

1. Array

Array assignment:
Array elements are numbered by continuous integers, starting from 0, followed by 1.Array assignmentThe same is true,Automatic expansion-"unlimited" principle, sequential.
For example, $ fred [0] = "aa"; $ fred [1] = "bb"; $ fred [10] = "gg "; the array fred now has a total of 11 elements (continuous, automatic expansion), other array elements that are not assigned values are usedUndef Filling.
Array reference:The reference is similar to the preceding array format. Note the following:
(1) If the reference table below exceeds the end of the array, the corresponding value will be undef.
(2) Special array index value: reference the value of the last element of the array: $ # bianlaing_ming or $ bianliang_ming [-1] (you canTail Loop).

2. List

List quantity:Parentheses, separated by commas. For the number list, you can also use the range OPERATOR:".."This operator counts from the number on the left to the right, and Adds 1 (not the unified conversion of numbers into numbers) each time to generate a series of continuous numbers. For example, (1.7,..., 5.7) indicates a list of five elements, 1, 2, 3, 4, and 5.
Qw Abbreviation:Create a simple word list. QW indicates quoted by whitspace (UseBlankCircle guide,Single quotesSeparate the words (word )). It extracts words by embedding spaces as separators to form a list.
From the first chapter, we can see that the characters in single quotes represent themselves. Perl also allows you to use any punctuation marks as delimiters. Commonly used methods include:
Qw! Fred barney betty wilma dino!
Qw/fred barney betty wilma dino/
Qw # fred barney betty wilma dino #
Qw {fred barney betty wilma dino}
Qw [fred barney betty wilma dino]
Qw <fred barney betty wilma dino>
The preceding statements are equivalent to qw (fred barney betty wilma dino. -- This is more consistentPerl's motto: There are more than one method (There's more than one way to do it).
Qw Usage Details, can refer to: http://perlmeme.org/howtos/perlfunc/qw_function.html
Assignment of the list:
There are three assignment modes:
(1) {$ fred, $ barney, $ dino }={ "fil", "rub", "und"}; ------- one-to-one correspondence
(2) {$ fred, $ barney }={ "fil", "rub", "und" };--------- the left-less and right-more values are ignored.
(3) {$ fred, $ barney, $ dino }={ "fil", "rub"} ----- multiple variables on the left are set to undef.
Here is another method to reference the entire array: @ shuzuming (@: you can read it as "all of the": all, all ).