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PROGRAM TO IMPLEMENT RECURSIVE DESCENT PARSER

Posted By: Adalberto Fischer     Category: C++ Programming     Views: 12468

PROGRAM TO IMPLEMENT RECURSIVE DESCENT PARSER.

Code for PROGRAM TO IMPLEMENT RECURSIVE DESCENT PARSER in C++ Programming

#include <iostream.h>
#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <stdlib.h>


typedef struct treenode
{
    char info;
    treenode *left;
    treenode *right;
}node;


    node * proc_e(char input[],int &ssm);
    node * proc_t(char input[],int &ssm);
    node * proc_v(char input[],int &ssm);
    void traversal(node *temp);

void main()
{
    char input[20];
    int ssm=0;
    node *root;
    clrscr();

    cout<<endl<<"ENTER THE STRING TO BE PARSED:";
    cin>>input;

    root = proc_e(input,ssm);
    cout<<endl<<"CONTENTS OF THE PARSE TREE:";
    traversal(root);


    getch();
}


void traversal(node *temp)
{


   if(temp != NULL)
   {
    traversal(temp->left);
    cout<<temp->info;
    traversal(temp->right);
    }
}


//PROCEDURE FOR NT E:

node * proc_e(char input[],int &ssm)
{
    node *a,*b;

    a=proc_t(input,ssm);

    while(input[ssm]=='+')
    {
        ssm++;
        b=proc_t(input,ssm);

        node *temp;
        temp=new node; //(node*)malloc(sizeof(node));
        temp->info='+';
        temp->left=a;
        temp->right=b;

        a=temp;

    }

    return a;
}





//PROCEDURE FOR NT T:

node * proc_t(char input[],int &ssm)
{
    node *a,*b;

    a=proc_v(input,ssm);
    ssm = ssm + 1;

    while(input[ssm] == '*')
    {
        ssm++;

        b=proc_v(input,ssm);
        node *temp;

        temp=new node;//(node *)malloc(sizeof(node));
        temp->info='*';
        temp->left=a;
        temp->right=b;

        a=temp;
        ssm = ssm +1;
    }

    return a;


}



//PROCEDURE FOR NT V:

node * proc_v(char input[],int &ssm)
{
    node *a;

    if(input[ssm]=='I')
    {
        node *temp;
        temp=new node; //(node*)malloc(sizeof(node));
        temp->info='I';
        temp->left=NULL;
        temp->right=NULL;
        return temp;
    }
    else
    {
        cout<<endl<<"ERROR. INVALID SYMBOL "<<input[ssm];
        getch();
        exit(0);
    }
}
  
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Adalberto Fischer
Adalberto Fischer author of PROGRAM TO IMPLEMENT RECURSIVE DESCENT PARSER is from Frankfurt, Germany.
 
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