III Parser

#include <iostream>
#include <cctype>
#include <cstdio>
#include <fstream>

using namespace std;

typedef enum TSymbolType {
    intconst, text, semicolon, period, quotas, othersy
} TSymbol;

char Char;
TSymbol Symbol;
char Spelling[9];
const int MAXLENGTH = 8;
int Constant;
const int MAXINTEGER = 1000000;
ifstream inputFile("C:\\Users\\Aleksandar\\source\\repos\\Parser\\Parser\\input.txt");

void GetNextChar() {
    if (!inputFile.is_open()) {
        fprintf(stderr, "Error: Unable to open input file\n");
        return;
    }
    Char = inputFile.get();
}

void error(const char* message) {
    fprintf(stderr, "Error: %s\n", message);
}

void GetNextSymbol() {
    int digit;
    int k = 0;
    while (!inputFile.eof() && !isdigit(Char) && Char != '\"' && Char != ';' && Char != '.' && !isalpha(Char)) {
        GetNextChar();
    }
    if (inputFile.eof()) {
        Char = '\0';
    }
    while (Char == ' ') {
        GetNextChar();
    }
    switch (toupper(Char)) {
    case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G':
    case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N':
    case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U':
    case 'V': case 'W': case 'X': case 'Y': case 'Z': {
        do {
            if (k < MAXLENGTH) {
                Spelling[k] = Char;
                k++;
            }
            GetNextChar();
        } while ((Char >= 'A' && Char <= 'Z') || (Char >= '0' && Char <= '9'));
        Spelling[k] = '\0';
        if (k > 8) {
            error("String is too long!");
        }
        Symbol = text;
        cout << "Text: " << Spelling << endl;
    } break;
    case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': {
        Constant = 0;
        do {
            digit = Char - '0';
            if ((Constant < (MAXINTEGER / 10)) || ((Constant == (MAXINTEGER / 10)) && (digit <= (MAXINTEGER % 10)))) {
                Constant = (10 * Constant) + digit;
            }
            else {
                error("Int constant too large!");
                Constant = 0;
            }
            GetNextChar();
        } while (Char >= '0' && Char <= '9');
        Symbol = intconst;
        cout << "Integer: " << Constant << endl;
    } break;
    case '.': {
        Symbol = period;
        GetNextChar();
        cout << "Period" << endl;
        return;
    }
    case ';': {
        Symbol = semicolon;
        GetNextChar();
        cout << "Semicolon" << endl;
    } break;
    case '\"': {
        Symbol = quotas;
        GetNextChar();
        int insideQuote = 0;
        while (insideQuote < 8 && Char != '\"') {
            Spelling[insideQuote] = Char;
            insideQuote++;
            GetNextChar();
        }
        if (Char == '\"') {
            Spelling[insideQuote] = '\0';
            cout << "String: " << Spelling << endl;
            GetNextChar();
        }
        else {
            error("String is too long or missing closing double quote(s)!");
            Spelling[insideQuote] = '\0';
            cout << "String: " << Spelling << endl;
        }
    } break;
    case '\0': {
        if (Symbol != othersy) {
            Symbol = othersy;
            cout << "End of Input" << endl;
        }
        break;
    }
    default: {
        Symbol = othersy;
        cout << "Unknown Symbol with ASCII value: " << static_cast<int>(Char) << endl;
        GetNextChar();
        break;
    }
    }
}

int accept(TSymbol symbol) {
    if (Symbol == symbol) {
        GetNextSymbol();
        return 1;
    }
    return 0;
}

int expect(TSymbol symbol) {
    if (accept(symbol)) {
        return 1;
    }
    error("Unexpected symbol!");
    return 0;
}

void Field() {
    if (accept(intconst) || accept(quotas) || accept(text)) {
        return;
    }
    else if (accept(period)) {
        accept(quotas);
        if (Symbol == text) {
            Field();
        }
        else {
            error("Expects text after period!");
        }
    }
    else if (Symbol != period && Symbol != othersy && Symbol != '\0') {
        error("Expects intconst, string, text, period, or end of input!");
    }

}

void Record() {
    Field();
    while (Symbol == period) {
        accept(period);
        Field();
    }
    if (!(Symbol == semicolon || Symbol == othersy || Symbol == '\0')) {
        error("Expects semicolon or end of input after the last field!");
    }
    if (Symbol == semicolon) {
        accept(semicolon);
    }
}

void DataFile() {
    Record();
    while (Symbol != othersy) {
        Record();
    }
    inputFile.close();
}

int main() {
    GetNextChar();
    GetNextSymbol();
    DataFile();
    return 0;
}