Program to parse a string using Operator Precedence parsing in C++.
#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
int Operator_Position_Finder(char );
#define node struct Basic_tree
int T4Tutorials[5][5]={
{1,0,0,1,1},
{1,1,0,1,1},
{0,0,0,2,3},
{1,1,3,1,1},
{0,0,0,3,2}};
int tos=-1;
void T4Tutorials_value(void);
//node create_node(char,*node);void DisplayTree( node *);
int isOperator(char );
struct Basic_tree
{
char data;
node *lptr;
node *rptr;
}*first;
struct opr
{
char op_name;
node *t;
}oprate[50];
char current_operators[5]={'+','*','(',')','['};
char OperatorsInStack[5]={'+','*','(',')',']'};
void main()
{
char exp[10];
int myVariable=0,row=0,col=0;
node *temp;
// clrscr();
printf("Enter Exp : ");
scanf("%s",exp);
T4Tutorials_value();
while(exp[myVariable] != '\0')
{
if(myVariable==0)
{
tos++;
oprate[tos].op_name = exp[tos];
}
else
{
if(isOperator(exp[myVariable]) == -1)
{
oprate[tos].t = (node*) malloc (sizeof(node));
oprate[tos].t->data = exp[myVariable];
oprate[tos].t->lptr = '\0';
oprate[tos].t->rptr = '\0';
}
else
{
row = Operator_Position_Finder(oprate[tos].op_name);
col = Operator_Position_Finder(exp[myVariable]);
if(T4Tutorials[row][col] == 0)
{
tos++;
oprate[tos].op_name = exp[myVariable];
}
elseif(T4Tutorials[row][col] == 1)
{
temp = (node*) malloc (sizeof(node));
temp->data = oprate[tos].op_name;
temp->lptr = (oprate[tos-1].t);
temp->rptr = (oprate[tos].t);
tos--;
oprate[tos].t = temp;
myVariable--;
}
elseif(T4Tutorials[row][col] == 2)
{
//temp = (node*) malloc (sizeof(node));
temp = oprate[tos].t;
tos--;
oprate[tos].t = temp;
}
elseif(T4Tutorials[row][col] == 3)
{
printf("\nExpression is Invalid...\n");
printf("%c %c can not occur simultaneously\n",oprate[tos].op_name,exp[myVariable]);
break;
}
}
}
myVariable++;
}
printf("show tree \n\n\n");
DisplayTree(oprate[tos].t);
printf("Over");
getch();
getch();
}
int isOperator(char c)
{
int i=0;
for(i=0;i<5;i++)
{
if (c==current_operators[i] || c==OperatorsInStack[i])
break;
}
if(i==5)
return (-1);
elsereturn i;
}
int Operator_Position_Finder(char c)
{
int i;
for(i=0;i<5;i++)
{
if (c==current_operators[i] || c==OperatorsInStack[i])
break;
}
return i;
}
void DisplayTree(node *start)
{
if(start->lptr != NULL)
DisplayTree(start->lptr);
if(start->rptr != NULL)
DisplayTree(start->rptr);
printf("%c \n",start->data);
}
void T4Tutorials_value(void)
{
int i,j;
printf("OPERATOR PRECEDENCE Matrix\n");
printf("===========================\n ");
for(i=0; i<5; i++)
{
printf("%c ",OperatorsInStack[i]);
}
printf("\n");
for(i=0;i<5;i++)
{
printf("%c ",current_operators[i]);
for(j=0;j<5;j++)
{
if(T4Tutorials[i][j] == 0)
printf("< ");
elseif(T4Tutorials[i][j] == 1)
printf("> ");
elseif(T4Tutorials[i][j] == 2)
printf("= ");
elseif(T4Tutorials[i][j] == 3)
printf(" ");
}
printf("\n");
}
}
Output
