Question

C++ Question

The first phase of compilation is called scanning or lexical analysis. This phase interprets the input program as a sequence of characters and produces a sequence of tokens, which will be used by the parser.

Write a C++ program that implements a simple scanner for a source file given as a command-line argument. The format of the tokens is described below. You may assume that the input is syntactically correct. Optionally, your program can build a symbol table (a hash table is a good choice), which contains an entry for each token that was found in the input. When all the input has been read, your program should produce a summary report that includes a list of all the tokens that appeared in the input, the number of times each token appears in the input and the class of each token. Your program should also list how many times tokens of each category appeared in the input.

Sample token format:

        keyword -> if | then | else | begin | end

        identifier -> character | character identifier

        integer -> digit | digit integer

        real -> integer.integer

        special -> ( | ) | [ | ] | + | - | = | , | ;

        digit -> 0|1|2|3|4|5|6|7|8|9

        character -> a|b|c ... |z|A|B|C ... |Z

Answer 1

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<stdio.h>
#include<string>
#include<map>
#include<vector>
#include<fstream>
#include<cstring>
#include<string.h>
#include<functional>

using namespace std;

map<string, int> classes = {{"keyword",0},{"identifier",0},{"digit",0},{"integer",0},{"real",0},{"character",0},{"alpha",0}};
vector<string> ints = {"0","1","2","3","4","5","6","7","8","9"};
vector<string> key_words = {"if","else","then","begin","end"};
vector<string> identi_fiers = {"(",")","[","]","+","=",",","-",":"};
vector<string> alpha_bets = {"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
vector<std::string>::iterator iters;

bool is_keyword(string ch);
bool is_identifier(char ch);
bool is_integer(char ch);
bool is_digit(string ch);
bool is_real(string ch);
bool is_char(string ch);
bool is_alpha(char ch);

int cnt_key = 0,cnt_ident =0,cnt_digit = 0,cnt_int = 0,cnt_alpha = 0,cnt_char = 0,cnt_real =0;

bool is_keyword(string ch)
{
   iters = find(key_words.begin(),key_words.end(),ch);
   if(iters != key_words.end()){
       classes["keyword"]++;
       return true;
   }  
   else{
       return false
   }
}

bool is_identifier(string ch)
{
   iters = find(identi_fiers.begin(),identi_fiers.end(),ch);
   if(iters != identi_fiers.end()){
       classes["identifier"]++;
       return true;
   }  
   else{
       return false
   }
}  

bool is_digit(string ch)
{
   iters = find(ints.begin(),ints.end(),ch);
   if(iters != ints.end()){
       classes["digit"]++;
       classes["integer"]++;
       return true;
   }  
   else{
       return false
   }
}  

bool is_integer(string ch)
{
   char *p;
   strtol(ch.c_str(), &p , 10);
   if(*p == 0){
       classes["digit"]++;
       return true;
   }  
   else{
       return false
   }
}  

bool is_real(string ch)
{
   bool isreal=false;
   if(ch.find(".") != std::string::npos){
       for(int j=0;j<ch.length;j++){
           if(ch[j] != '.'){
               string search;
               search = ch[j];
               iters = find(ints.begin(),ints.end(),search);
               if(iters != ints.end()){
                   isreal = true;
               }
               else{
                   isreal = false;
               }
           }
   else{;}
       }
   }  
   else {;}
       if(isreal == true){
           classes["real"]++;
       return true;}
       else {return false;}
}

bool is_alpha(string ch)
{
   iters = find(alpha.begin(),alpha.end(),ch);
   if(iters != alpha.end()){
       classes["alpha"]++;
       classes["char"]++;
       return true;
   }  
   else{
       return false
   }
}  

bool is_char(string ch)
{
   bool ischar = false;
   for(int i=0;i<ch.length();i++){
       if(isalpha(ch[i])
           ischar = true;
       else
           ischar = false;
   }
   if(ch.length() >1 && ischar ==true)
   {
       classes["char"]++;
   return true;}      
   else{
       return false
   }
}  

int main(int argc, char *argv[])
{
   int token_cnt = 0; //used to count tokens as they are read.
  
   //atleast one commandline argument must be supplied
   if(argc < 2)
   {
       cerr <<"Error: filename argument not given" <<endl;
       exit(1);
   }
  
   ifstream in_File(argv[1], ios::in) //open file for input.
  
   //check for errors in opening the file
   if(!in_File){
       cerr <<"File" <<argv[1] << "counld not be opened" <<endl;
       exit(1);
   }
  
  
   char lines[100]; //char array used to hold lines of text input
   char *ps; //pointer used to tokenize string
  
   while(in_File.getline(lines,100)){ //reads upto 100chars into lies array
       ps = strtok(lines, " ~'!@#$^&*_{}:<>|?"); //assigns tokenpointer to first token in line
       while(ps != NULL){
           if(is_keyword(ch)){
               cnt_key++;
           }
           else if (isIdentifier(ps)) {
               cnt_ident++; }
           else if (is_char(ps)) {
               cnt_char++; }
           else if (is_digit(ps)) {
               cnt_digit++; }
           else if (is_integer(ps)) {
               cnt_int++; }
           else if (is_real(ps)) {
               cn++; }
           else if (is_alpha(ps)) {
               cnt_alpha++; }
           else {;}
           ps = strtok(lines, " ~'!@#$^&*_{}:<>|?"); //assigns tokenpointer to first token in line
       }
   }
  
std::cout << "CLASS" <<"keyword" <<":" <<classes["keyword"] <<"\n";
std::cout << "CLASS" <<"identifier" <<":" <<classes["identifier"] <<"\n";
std::cout << "CLASS" <<"digit" <<":" <<classes["digit"] <<"\n";
std::cout << "CLASS" <<"integer" <<":" <<classes["integer"] <<"\n";
std::cout << "CLASS" <<"character" <<":" <<classes["char"] <<"\n";
std::cout << "CLASS" <<"alphabet" <<":" <<classes["alpha"] <<"\n";
std::cout << "CLASS" <<"real" <<":" <<classes["real"] <<"\n";
  

in_File.close();
return 0;
}