How to implement a stack in Perl

In Perl, the stack is a linear data structure that follows LIFO (last in, first out) or FILO (first in, first out) order; so how to implement a stack? The following article will introduce to you how to implement a stack in Perl. I hope it will be helpful to you.

How to create a stack?

Simply put, a stack is an array where insertions and deletions occur only at one end called the top of the stack.

Creating a stack in Perl is very simple. All we need to do is declare an array.

Example:

Create a stack that may be empty:

@stack;

Or you can initialize it:

@stack = (1, 2, 3);

How about in the stack Push?

Pushing is a process of inserting elements into the stack. Pushing can be done using the push() function or the splice() function.

1. Use push() to push:

Basic syntax:

push（@stack，list）;

Parameters:

● @stack: The stack to be pushed.

● List: Elements to be pushed onto the stack. These elements may be scalars, arrays, hashes, or any combination of these elements.

Example:

#初始化堆栈
@stack = (1..3); 
  
#输出原始栈
print "原始栈： @stack"; 
  
#要推送的标量
$scalar = "scalar"; 
  
# 要推送的数组
@array = ("a", "r", "r", "a", "y"); 
  
# 要推送的哈希
%hash = ("PHP" => 10,  
         "Perl" => 20); 
           
# 可以同时插入标量、数组和哈希
push(@stack, ($scalar, @array, %hash));  
  
# 推送操作后更新堆栈
print("\n更新后的堆栈：@stack");

Output:

原始栈：1 2 3
更新后的堆栈：1 2 3 scalar  a r r a y PHP 10 Perl 20

2. Use splice() to push:

Basic syntax:

splice(@stack, scalar(@stack), 0, list);

Parameters:

● The splice() function appends 'list' to the end of @stack.

●　'list' can be a scalar, array or hash.

Example:

#初始化堆栈
@stack = (1..3); 
  
#输出原始栈
print "原始栈： @stack"; 
  
#要推送的标量
$scalar = "scalar"; 
  
# 要推送的数组
@array = ("h", "e", "l", "l", "o"); 
  
# 要推送的哈希
%hash = ("PHP" => 10,  
         "Perl" => 20); 
  
# 可以同时插入标量、数组和哈希
splice(@stack, scalar(@stack), 0,  
       ($scalar, @array, %hash)); 
         
#  推送操作后更新堆栈
print("\n更新后的堆栈：@stack");

Output:

原始栈：1 2 3
更新后的堆栈：1 2 3 scalar h e l l o PHP 10 Perl 20

How to implement pop in the stack?

In the stack, popping is the process of deleting the topmost element of the stack; popping can be completed using the pop() function or splice() function.

1. Use the pop() function to achieve pop-up:

Basic syntax:

$popped_element = pop(@stack);

Parameters:

● pop() The function returns the popped element.

●　$ popped_element contains the element popped from the stack.

Example:

# 初始化堆栈
@stack = (1..3); 
  
# 原始栈
print "原始栈： @stack"; 
  
# 移除并返回最上面的元素，即3。
$popped_element = pop(@stack);  
  
# 输出弹出元素
print "\n弹出元素：$popped_element"; 
         
# 弹出操作后更新堆栈
print("\n更新后的堆栈：@stack");

Output:

原始堆栈：1 2 3
弹出元素：3
更新后的堆栈：1 2

Note: If the stack is empty, undef is returned. undef is similar to NULL in Java and None in Python. However, no error is thrown.

2. Use the splice() function to pop up:

Basic syntax:

$popped_element=splice(@stack, -1);

Parameters:

● splice() function Removes the last element of the stack and returns it.

●　$popped_element: Stores the returned value.

Example:

# 初始化堆栈
@stack = (1..3); 
  
# 原始栈
print "原始栈： @stack"; 
  
# 使用splice()函数弹出
$popped_element = splice(@stack, -1); 
  
# 输出弹出元素
print "\n弹出元素：$popped_element"; 
         
# 弹出操作后更新堆栈
print("\n更新后的堆栈：@stack");

Output:

原始堆栈：1 2 3
弹出元素：3
更新后的堆栈：1 2

Note: If the stack is empty, an error is raised.

Related video tutorial recommendations: "Perl Tutorial"

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