Parser

/*
GRAMAR FOR SYNATX CHECKING OF FUNCTION PROTOTYPE

fun_pro -> ret_type fun_name ( arg_list );
ret_type -> int | char | float
fun_name -> [a-zA-Z]+
arg_list -> ret_type fun_name
| ret_type fun_name , arg_list

*/

#include "stdafx.h"
#include <stdio.h>
#include <string.h>
void getToken(FILE *read);
char word[50];
FILE *ptr;
void fun_pro();
void ret_type();
void fun_name();
void arg_list();

int main(int argc, char* argv[])
{

ptr = fopen("sample.txt","r");

if (ptr==NULL)
{
printf("Not able to load file\n");
return(0);
}
fun_pro();

return 0;
}

void getToken(FILE *read)
{
char ch;
int i=0;

while ((ch = fgetc(read))!=EOF)
{
if (ch != ' ' && ch !='\t')
{
fseek(read,-1,SEEK_CUR);
break;
}
}

while ((ch=fgetc(read))!=EOF)

{
if (ch != ' ' && ch != '\t' && ch != '\n' && ch != '(' &&
ch != ')' && ch !=',' && ch !=';' )
word[i++] = ch;
else
{
if (ch == '(' || ch == ')' || ch == ',' || ch == ';')
{
if (i==0)
word[i++] = ch;
else
fseek(read,-1,SEEK_CUR);
}
break;
}
}
word[i] = '\0';
}

void fun_pro()
{
getToken(ptr);

ret_type();
fun_name();

if (strcmp("(",word) == 0)

getToken(ptr);

else
{
printf (" open paranthesis is missing\n");
return;
}
arg_list();

if (strcmp(")",word) == 0)

getToken(ptr);

else
{
printf (" close paranthesis is missing\n");
return;
}

if (strcmp(";",word) == 0)
{
getToken(ptr);

}

else
{

printf (" semicolon is missing\n");
return;
}

printf("Valid function prototype\n");
}

void ret_type()
{

if (strcmp("int",word) == 0 || strcmp("void",word) == 0 ||
strcmp("char",word) == 0 || strcmp("float",word) == 0)
getToken(ptr);
else
printf("Invalid return type\n");
}

void fun_name()
{
int i;

for (i =0; word[i]!='\0';i++)
{
if ( (word[i] >= 97 && word[i] <= 122 ) || (word[i] >= 65
&& word[i] <= 90 ) )

continue;
else
{
printf ("Not a valid identifier\n");
break;
}

}
getToken(ptr);
}

void arg_list()
{

if ((strcmp(")",word))==0)
{
printf ("No arguments\n");
fseek(ptr,-1,SEEK_CUR);

}
else
{
ret_type();
fun_name();

if (strcmp(",",word)==0)
{
getToken(ptr);

arg_list();
}
}

}