Top Down Recursive Decent Parser

Compiler Construction Lab Manual / Top Down Recursive Decent Parser

Program Name

Write a Compiler Construction Program for Top Down Recursive Decent Parser.

Theory
Implementation of Top Down Recursive Decent Parser used to check the syntax.

Program Code


#include<stdio.h>
#include<stdlib.h>
#include<math.h>
char token;
void expr();
void term();
void factor();
void match(char);
int main()
{
token=getchar();
expr();
if(token=='\n')
printf("SUCCESS\n");
else{printf("ERROR\n");exit(1);}
}

void match(char etoken)
{
if(token==etoken)
token=getchar();
else{printf("error\n");exit(1);}
}

void expr()
{
term();
if(token=='+'){match('+');expr();}
}

void term()
{
factor();
if(token=='*'){match('*');term();}
}

void factor()
{
if(token=='('){match('(');expr();match(')');}
else if(isdigit(token))
match(token);
else{printf("error1\n");exit(1);}
}

Saving: vi rd.c

Compiling and Running
cc rd.c
./a.out

Input
2+3
SUCCESS

Output
2++
error1

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