Chapter 6.7: An Example: A Singly Linked List

Adapted from: “Object-Oriented Programming Using C++” by Ira Pohl (Addison - Wesley)

Program that demonstrates a singly linked list using classes in C++

In file slist.cpp

/*********************************************************************

  Filename:  slist.cpp
  Chapter:   6      Object Creation and Destruction
  Section:   6.7    An Example:  A Singly Linked List
  Compiler:  Borland C++     Version 5.0       Summer 1996
  Object Oriented Programming Using C++, Edition 2   By Ira Pohl

*********************************************************************/

//A singly linked list

#include <iostream>         // Changed iostream.h to iostream. MK.
#include <assert.h>

using namespace std;       // Added. MK.

struct slistelem {
   char       data;
   slistelem*  next;
};

class slist { //a singly linked list
public:
   slist() : h(0) { };        //0 denotes empty slist
   ~slist();                  // alternative { release(); }
   void  prepend(char c);     //adds to front of slist
   void  del();
   slistelem*  first() const { return h; };
   void  print() const;
   void  release();
private:
   slistelem*  h;           //head of slist
};


void slist::prepend(char c)
{
   slistelem*  temp = new slistelem;//create element
   assert(temp != 0);
   temp -> next = h;                //link to slist
   temp -> data = c;
   h = temp;                 //update head of slist
}

void slist::del()
{
   slistelem*  temp = h;

   h = h -> next;     //presumes an non-empty slist
   delete temp;
}

void slist::print() const   //object is unchanged
{
   slistelem*  temp = h;

   while (temp != 0) {     //detect end of slist
      cout << temp -> data << " -> ";
      temp = temp -> next;
   }
   cout << "\n###" << endl;
}

//elements returned to free store
void slist::release()
{
   while (h != 0)
      del();
}

slist:: ~slist()
{
   cout << "destructor invoked" << endl;
   release();
}

int main()
{
   slist*  p;
   {
      slist  w;

      w.prepend('A');
      w.prepend('B');
      w.print();
      w.del();
      w.print();
      p = &w;
      p -> print();
      cout << "exiting inner block" << endl;
   }
   //p -> print();  gives system dependent behavior
   cout << "exiting outer block" << endl;
}

Compilation Process

The above program is compiled and run using Gnu Compiler Collection (g++):

import os
root_dir = os.getcwd()

code_dir = root_dir + "/" + \
    "Cpp_Code/Chapter_6_7_An_Example__A_Singly_Linked_List"

os.chdir(code_dir)

build_command = os.system("g++ slist.cpp -w -o slist")

Execution Process

exec_status = os.system("./slist")

B -> A -> 
###
A -> 
###
A -> 
###
exiting inner block
destructor invoked
exiting outer block