// Lab Problem 5A - file "varlist.h"

// SE307 CCT

// T Naughton, CS NUIM, tomn@cs.may.ie

// Last updated 1 November 2000

#include<iostream>

#include<string>



#ifndef VARLIST_H

#define VARLIST_H



/* This class maintains a dynamic list of variables for machines

** simulating/analysing the code of another machine passed to it

** as input. The methods of this class are chosen to reflect the

** capabilities of the restricted language defined in lab sheet 4.

*/



class VarDetails {



 // a simple class defining the contents of each list element

 public:

  string name;

  int value;

  VarDetails * next; // link to next element



};





class VarList {



  VarDetails * head; // head of the linked list



 public:

  VarList();

  ~VarList();



  void DeleteList();

  void Add(string varname, int initval);

  VarDetails * FindElement(string varname);

  void Inc(string varname);

  void Set(string varname, int newval);

  bool LessThan(string var1, string var2);

  int Val(string varname);

  bool Contains(string varname);

  void PrintList();



};





VarList::VarList() {



  head = NULL; // mark the end of the list with a NULL



}





VarList::~VarList() {



  DeleteList(); // clean up

}





void VarList::DeleteList() {



  /* Delete the entire list.

  */

  VarDetails * temp; // pointer to element to be deleted



  while (head != NULL) {

    temp = head;

    head = head->next;

    delete temp;

  }

  // head will have been set to NULL when loop terminates.



}





void VarList::Add(string varname, int initval) {



  /* Add a new variable to the list of variables. Initialise

  ** to initval.

  */

  VarDetails * temp;



  temp = new VarDetails;

  temp->name = varname;

  temp->value = initval;



  temp->next = head; // add to head of list

  head = temp;



}





VarDetails * VarList::FindElement(string varname) {



  /* Return a pointer to the appropriate list element if it

  ** exists, else print an error message and return NULL.

  */

  VarDetails * temp;



  temp = head;



  while (temp != NULL) {



    if (temp->name == varname) {



      return temp;



    }

    temp = temp->next;

  }



  cout << "\nError: Variable " << varname << " has not been"

       << " declared and so cannot be accessed." << endl;

  return NULL;

}





void VarList::Inc(string varname) {



  /* Increment the value in a particular variable.

  */

  VarDetails * temp;



  temp = FindElement(varname);

  if (temp != NULL) {



    temp->value = temp->value + 1;

  }



}





void VarList::Set(string varname, int newval) {



  /* Update the value of varname in the list.

  */

  VarDetails * temp;



  temp = FindElement(varname);

  if (temp != NULL) {



    temp->value = newval;

  }



}





bool VarList::LessThan(string var1, string var2) {



  /* Return true if the value in var1 is less than the value

  ** in var2, otherwise return false.

  */

  VarDetails * temp;

  int a; // holds the value of var1



  temp = FindElement(var1);

  if (temp != NULL) {

    a = temp->value;



    temp = FindElement(var2);

    if (temp != NULL) {



      return (a < temp->value);

    }



  }



  return false;

}





int VarList::Val(string varname) {



  /* Return the value of varname.

  */

  VarDetails * temp;



  temp = FindElement(varname);

  if (temp != NULL) {



    return (temp->value);



  } else {



    return -1;



  }



}





bool VarList::Contains(string varname) {



  /* Returns true if varname is in the list of variables, else

  ** returns false.

  */

  return (FindElement(varname) == NULL);



}





void VarList::PrintList() {



  /* Print all variables and values.

  */

  VarDetails * temp;



  cout << "   \t// ";

  temp = head;

  while (temp != NULL) {



    cout << temp->name << '=' << temp->value << ' ';

    temp = temp->next;

  }

  cout << flush;



}



#endif