If/Else with Parser/Tokens?

[al3x57]

Any help to lead me in the right direction will be greatly appreciated!
The error is in the 'main' section.
The following are some tests... I can only get a couple of them to work. I know I have it set up wrong. Can someone tell me what I'm doing wrong? Thank you!
int A;
no error found

int a;
illegal variable name

short B;
unrecognizable type

float C = 0.5;
no error found

int A = 10,
unexpected token

short D;
unrecognizable type

float F;
illegal variable name

#include <iostream>
#include <string>
using namespace std;
string GetToken();
void error(int);

int main() {
	string token;
	cout << "Please enter a declaration in format "
		<< "<type> <variable> [= number];" << endl;

	token = GetToken();

	if (token == "int" + 'A' + ';' || token == "int" + 'B' + ';' || token == "int" + 'C' + ';' ||
			token == "int" + 'D' + ';' || token == "int" + 'E' + ';')
		{
			error(0);
		}
       else if (token == "int" + 'a' + ';' || token == "int" + 'a' + ';' || token == "int" + 'c' + ';' ||
			token == "int" + 'd' + ';' || token == "int" + 'e' + ';')
		{
			error(2);
		}
       else if (token == "int" + 'A' + ',' || token == "int" + 'B' + ',' || token == "int" + 'C' + ',' ||
			token == "int" + 'D' + ',' || token == "int" + 'E' + ',')
		{
			error(4);
		}
	else if (token == "float")
	{
		if (token == token + 'A' || token == token + 'B' || token == token + 'C' ||
			token == token + 'D' || token == token + 'E')
		{
			error(0);
		}
		else if (token == "float" + 'F')
		{
			error(2);
		}
	}
	else if (token != "float" && token != "int")
	{
		error(1);
	}

	system("pause");
	return 0;
}

string GetToken() {
	string token;
	string errors;
	bool theToken = true;
	char ch;

	while (theToken == true)
	{
		cin.get(ch);

		while (ch == ' ')
		{
			cin.get(ch);
		}

		if (isdigit(ch))
		{

			while (isdigit(ch))
			{
				token = token + ch;
				cin.get(ch);
				if (ch == '.')
				{
					token = token + ch;
					cin.get(ch);
				}

				if (ch == ';')
				{
					token = token + '\n' + ch;
					cin.get(ch);
				}
				if (ch == '#')
				{
					token = token + '\n' + ch + ':' + " Error: Unrecognizable token";
				}
			}
			theToken = false;
		}
		else
		{
			token = token + ch;

			if (token == "i")
			{
				theToken = true;
			}
			else if (token == "in")
			{
				theToken = true;
			}
			else if (token == "int")
			{
				theToken = false;
			}
			else if (token == "f")
			{
				theToken = true;
			}
			else if (token == "fl")
			{
				theToken = true;
			}
			else if (token == "flo")
			{
				theToken = true;
			}
			else if (token == "floa")
			{
				theToken = true;
			}
			else if (token == "float")
			{
				theToken = false;
			}
			else if (token == "A" || token == "B" || token == "C" || token == "D" || token == "E")
			{
				theToken = false;
			}
			else if (token == "=")
			{
				theToken = false;
			}
			else if (token == ";")
			{
				theToken = false;
			}
			else if (token == "\n")
			{
				token = "";
				theToken = false;
			}
			else
			{
				token = token + ':' + " Error: Unrecognizable token";
				theToken = false;
			}
		}

	}

	return token;
}

void error(int code)
{
	switch (code) {
	case 0: cout << "no errors found" << endl; break;
	case 1: cout << "unrecognizable type" << endl; break;
	case 2: cout << "illegal variable name" << endl; break;
	case 3: cout << "unexpected number" << endl; break;
	case 4: cout << "; expected" << endl;
	}
	return;
}

[al3x57]

string token;
	cout << "Please enter a declaration in format "
		<< "<type> <variable> [= number];" << endl;

	//token = GetToken();
	getline(cin, token);

	if (token == "int A;" || token == "float C = 0.5;" || token == "float B;" || token == "float C = 0.2;")
	{
		error(0);
	}
	else if (token == "int a;" || token == "float F;")
	{
		error(1);
	}
	else if (token == "short B;" || token == "short D;")
	{
		error(2);
	}
	else if (token == "int A = 10,")
	{
		error(4);
	}

This is a lot easier lol, but I know this isn't the point of problem... I just don't understand how to evaluate errors in the string based on the tokens... Grrrr.

[salem c]

int A;
no error found

int a;
illegal variable name

float F;
illegal variable name

So do you have an grammar which you're expected to validate?
See https://en.wikipedia.org/wiki/Syntax_(programming_languages)

For example, on what basis is 'A' a valid variable name and 'F' is not a valid variable name.

> token == "float C = 0.5;"
So by your reckoning, "float C = 0.6;" is wrong?

Is "int A = 42;" valid or invalid?
Is "int A = 1.23;" valid or invalid?

[al3x57]

Yes, the grammar is as follows:

// <declaration> 	::= 	<type>  <var> ’;’ | <type> <var> ’=’ <number> ’;’
// <type> 		::= 	int | float
// <var> 		::= 	A | B | C | D | E
// <number> 	::= 	<integer> | <float>
// <integer> 	::= 	<integer> <digit> | <digit>
// <digit> 		::= 	0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
// <float> 		::= 	<integer> ‘.’ <integer> 

The first part of the problem was getting the grammar set up and it taking the token, now I'm struggling with the parser.

[jonnin]

two things:
first, it would be a lot easier if you used a map of the tokens instead of all that if-then logic
and second, a boolean is either true or false.
default one of them; either its initialized false and you check the things that can set it to true, or its initialize to true and check the things that can make it false.
you don't need both sides of the equation, it just bloats the code even more.

but if you use the map, its either in the map (set to true) or not in the map (default false) which would boil your code down to a couple of lines... 90-150 roughly would just be
bool tok = false;
if token in map
tok = true