Write a program to make a simple lexical analyzer that will build a symbol table from given stream of chars. You will need to read a file named “input.txt” to collect all chars. For simplicity, input file will be a C/Java/Python program without headers and methods(body of the main progrm). Then you will identify all the numerical values, identifiers, keywords, math operators, logical operators and others[distinct]. See the example for more details. You can assume that, there will be a space after each keyword.
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main(){
/* By Ashik Rabbani
Daffodil International University,CSE43 */
keyword_check();
identifier_check();
math_operator_check();
logical_operator_check();
numerical_check();
others_check();
return 0;
}
void math_operator_check()
{
char ch, string_input[15], operators[] = "+-*/%";
FILE *fp;
char tr[20];
int i,j=0;
fp = fopen("input.txt","r");
if(fp == NULL){
printf("error while opening the file\n");
exit(0);
}
printf("\nMath Operators : ");
while((ch = fgetc(fp)) != EOF){
for(i = 0; i < 6; ++i){
if(ch == operators[i])
printf("%c ", ch);
}
}
printf("\n");
fclose(fp);
}
void logical_operator_check()
{
char ch, string_input[15], operators[] = "&&||<>";
FILE *fp;
char tr[20];
int i,j=0;
fp = fopen("input.txt","r");
if(fp == NULL){
printf("error while opening the file\n");
exit(0);
}
printf("\nLogical Operators : ");
while((ch = fgetc(fp)) != EOF){
for(i = 0; i < 6; ++i){
if(ch == operators[i])
printf("%c ", ch);
}
}
printf("\n");
fclose(fp);
}
void numerical_check()
{
char ch, string_input[15], operators[] ={'0','1','2','3','4','5','6','7','8','9'};
FILE *fp;
int i,j=0;
fp = fopen("input.txt","r");
if(fp == NULL){
printf("error while opening the file\n");
exit(0);
}
printf("\nNumerical Values : ");
while((ch = fgetc(fp)) != EOF){
for(i = 0; i < 6; ++i){
if(ch == operators[i])
printf("%c ", ch);
}
}
printf("\n");
fclose(fp);
}
void others_check()
{
char ch, string_input[15], symbols[] = "(){}[]";
FILE *fp;
char tr[20];
int i,j=0;
fp = fopen("input.txt","r");
if(fp == NULL){
printf("error while opening the file\n");
exit(0);
}
printf("\nOthers : ");
while((ch = fgetc(fp)) != EOF){
for(i = 0; i < 6; ++i){
if(ch == symbols[i])
printf("%c ", ch);
}
}
printf("\n");
fclose(fp);
}
void identifier_check()
{
char ch, string_input[15];
FILE *fp;
char operators[] ={'0','1','2','3','4','5','6','7','8','9'};
int i,j=0;
fp = fopen("input.txt","r");
if(fp == NULL){
printf("error while opening the file\n");
exit(0);
}
printf("\nIdentifiers : ");
while((ch = fgetc(fp)) != EOF){
if(isalnum(ch)){
string_input[j++] = ch;
}
else if((ch == ' ' || ch == '\n') && (j != 0)){
string_input[j] = '\0';
j = 0;
if(isKeyword(string_input) == 1)
{
}
else
printf("%s ", string_input);
}
}
printf("\n");
fclose(fp);
}
int isKeyword(char string_input[]){
char keywords[32][10] = {"auto","break","case","char","const","continue","default",
"do","double","else","enum","extern","float","for","goto",
"if","int","long","register","return","short","signed",
"sizeof","static","struct","switch","typedef","union",
"unsigned","void","volatile","while"};
int i, flag = 0;
for(i = 0; i < 32; ++i){
if(strcmp(keywords[i], string_input) == 0){
flag = 1;
break;
}
}
return flag;
}
void keyword_check()
{
char ch, string_input[15], operators[] = "+-*/%=";
FILE *fp;
char tr[20];
int i,j=0;
printf(" Token Identification using C \n By Ashik-E-Rabbani \n 161-15-7093\n\n");
fp = fopen("input.txt","r");
if(fp == NULL){
printf("error while opening the file\n");
exit(0);
}
printf("\nKeywords : ");
while((ch = fgetc(fp)) != EOF){
if(isalnum(ch)){
string_input[j++] = ch;
}
else if((ch == ' ' || ch == '\n') && (j != 0)){
string_input[j] = '\0';
j = 0;
if(isKeyword(string_input) == 1)
printf("%s ", string_input);
}
}
printf("\n");
fclose(fp);
}
