LOGIC: Read the input string. Write procedures for the non terminals Verify the next token equals to non terminals if it satisfies match the non terminal. If the input string does not match print error.
RESOURCE: Turbo C++
PROGRAM:
#include
#include
#include
char input[100];
int i,l;
void main()
{
clrscr();
printf("\nRecursive descent parsing for the following grammar\n"); printf("\nE->TE'\nE'->+TE'/@\nT->FT'\nT'->*FT'/@\nF->(E)/ID\n"); printf("\nEnter the string to be checked:");
gets(input);
if(E())
{
if(input[i+1]=='\0')
printf("\nString is accepted");
else
printf("\nString is not accepted");
}
else
printf("\nString not accepted");
getch();
}
E()
{
if(T())
{
if(EP())
return(1);
else
return(0);
}
else
return(0);
}
EP()
{
if(input[i]=='+')
{
i++;
if(T())
{
if(EP())
return(1);
else
return(0);
}
else
return(0);
}
else
return(1);
}
T()
{
if(F())
{
if(TP())
return(1);
else
return(0);
}
else
return(0);
}
TP()
{
if(input[i]=='*')
{
i++;
if(F())
{
if(TP())
return(1);
else
return(0);
}
else
return(0);
}
else
return(1);
}
F()
{
if(input[i]=='(')
{
i++;
if(E())
{
if(input[i]==')')
{
i++;
return(1);
}
else
return(0);
}
else
return(0);
}
else if(input[i]>='a'&&input[i]<='z'||input[i]>='A'&&input[i]<='Z')
{
i++;
return(1);
}
else
return(0);
}
INPUT & OUTPUT: Recursive descent parsing for the following grammar E->TE' E'->+TE'/@ T->FT' T'->*FT'/@ F->(E)/ID Enter the string to be checked:(a+b)*c String is accepted Recursive descent parsing for the following grammar E->TE' E'->+TE'/@ T->FT' T'->*FT'/@ F->(E)/ID
Enter the string to be checked:a/c+d
String is not accepted