Question

I’m trying to compile code in g++ and I get the following errors:

In file included from scanner.hpp:8,
from scanner.cpp:5:
parser.hpp:14: error: ‘Scanner’ does not name a type
parser.hpp:15: error: ‘Token’ does not name a type

Here’s my g++ command:

g++ parser.cpp scanner.cpp -Wall

Here’s parser.hpp:

#ifndef PARSER_HPP
#define PARSER_HPP
#include <string>
#include <map>
#include "scanner.hpp"
using std::string;


class Parser
{
// Member Variables
    private:
        Scanner lex;  // Lexical analyzer 
        Token look;   // tracks the current lookahead token

// Member Functions
    <some function declarations>
};

#endif

and here’s scanner.hpp:

#ifndef SCANNER_HPP
#define SCANNER_HPP

#include <iostream>
#include <cctype>
#include <string>
#include <map>
#include "parser.hpp"
using std::string;
using std::map;

enum
{
// reserved words
    BOOL, ELSE, IF, TRUE, WHILE, DO, FALSE, INT, VOID,
// punctuation and operators
    LPAREN, RPAREN, LBRACK, RBRACK, LBRACE, RBRACE, SEMI, COMMA, PLUS, MINUS, TIMES,
    DIV, MOD, AND, OR, NOT, IS, ADDR, EQ, NE, LT, GT, LE, GE,
// symbolic constants
    NUM, ID, ENDFILE, ERROR 
};


class Token
{
    public:
        int tag;
        int value;
        string lexeme;
        Token() {tag = 0;}
        Token(int t) {tag = t;}
};

class Num : public Token
{
    public:
        Num(int v) {tag = NUM; value = v;}
};

class Word : public Token
{
    public:
    Word() {tag = 0; lexeme = "default";}
        Word(int t, string l) {tag = t; lexeme = l;}
};


class Scanner
{
    private:
        int line;               // which line the compiler is currently on
        int depth;              // how deep in the parse tree the compiler is
        map<string,Word> words; // list of reserved words and used identifiers

// Member Functions
    public:
        Scanner();
        Token scan();
        string printTag(int);
        friend class Parser;
};

#endif

anyone see the problem? I feel like I’m missing something incredibly obvious.

Answer 1

parser.hpp incluser scanner.hpp and vice versa.

So one file evalated before the other.

You can use a forward declaration like

class Scanner;

or reorginaze your headers