Problem using case '\n': with an inputted char.

[Filthy_Utter]

I'm trying to search a specified file for all instances of substring "abbaa."

This is an easy problem, and I know I can do it better than I have, but the professor is making us use a 6x3 array in order to help us understand finite state machines.

Well the code I wrote runs perfectly, but the case for '\n' doesn't catch. It just flows through without it. Any ideas? (it's probably something extremely simple )

Thanks in advance!

Significant portion of code:

		if(fin)
		{
			fin >> inChar;
			while(fin)
			{
				switch(inChar)
				{
				case 'a':
					currentState = state[currentState][a];
					break;
				case 'b':
					currentState = state[currentState][b];
					break;
				case '\n':
					lineCount++;
					colCount = 0;
					currentState = state[currentState][other];
					break;
				default:
					currentState = state[currentState][other];
					break;
				}
				fin >> inChar;
				if(currentState == S5)
					cout << endl << "* line " << lineCount << ", column " << colCount - 4;
				colCount++;
			}
			quit = true;
		}

Program:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
	//declerations and definitions
	enum { S0, S1, S2, S3, S4, S5 };
	enum { a, b, other };

	fstream 
		fin;

	string
		file;

	char
		inChar;

	bool
		quit = false;

	int
		state[6][3], //6x3 array for state
		currentState = S0,
		lineCount = 1,
		colCount = 1;

	
	/*
	currentState = &state[*currentState][a];
	cout << *currentState;
	*/
	
	//define the array
	for(int i = S0; i <= S5; i++)
		state[i][other] = S0;
	
	state[S0][a] = S1;
	state[S1][a] = S1;
	state[S2][a] = S1;
	state[S3][a] = S4;
	state[S4][a] = S5;
	state[S5][a] = S1;

	state[S0][b] = S0;
	state[S1][b] = S2;
	state[S2][b] = S3;
	state[S3][b] = S0;
	state[S4][b] = S2;
	state[S5][b] = S2;
	
	while(quit == false)
	{
		//open the fin stream
		cout << "Please enter the input file:" << endl 
			 << "* ";
		cin >> file;
		fin.open(file,ios::in);

		//check for fin stream
		if(fin)
		{
			fin >> inChar;
			while(fin)
			{
				switch(inChar)
				{
				case 'a':
					currentState = state[currentState][a];
					break;
				case 'b':
					currentState = state[currentState][b];
					break;
				case '\n':
					lineCount++;
					colCount = 0;
					currentState = state[currentState][other];
					break;
				default:
					currentState = state[currentState][other];
					break;
				}
				fin >> inChar;
				if(currentState == S5)
					cout << endl << "* line " << lineCount << ", column " << colCount - 4;
				colCount++;
			}
			quit = true;
		}
		else
		{
			do
			{
				system("CLS");
				cout << "The input file was not opened successfully. Would you like to try again?" << endl
					 << "(y/n):" << endl 
					 << "* ";
				cin >> inChar;
				inChar = toupper(inChar);
			} 
			while(inChar != 'Y' && inChar != 'N');

			if(inChar == 'N')
				quit = true;
			system("CLS");
		}
	}
	cout << endl << endl;
	system("PAUSE");
	return 0;
}

Note: I know this code is pretty sloppy, but I've done it in just a few hours (most of which was trying to solve this bug). I will tidy it up later.
Note2: When I get better at coding I plan to contribute to this community instead of just asking questions all of the time!

[Paul McKenzie]

Well the code I wrote runs perfectly, but the case for '\n' doesn't catch. It just flows through without it. Any ideas? (it's probably something extremely simple )

Have you debugged your code using your compiler's debugger? What happens when the current character is a carriage return? What happens right before this (the very last character before the carriage return)? Is that processed successfully? If so, then use your debugger to step through the program to see what it does with the next character (the return).

Note2: When I get better at coding I plan to contribute to this community instead of just asking questions all of the time!

Programming isn't just about writing code and running code. It is also about debugging code that doesn't work. No programmer writes perfect code (unless the program is a toy program), so debugging is part and parcel of learning how to write programs.

Regards,

Paul McKenzie

[monarch_dodra]

istreams, by default, skip all manners of white spaces (space, tabs, carriages, etc...).

You can use std::noskipws if you need to take ws into account.

[Filthy_Utter]

Thanks Paul, I do try really hard to learn from my mistakes. I know it will pay off one day.
But, I had tried using the debugger and could not find out why it was skipping. It just wasn't catching.

Monarch's advice worked, however. I knew you couldn't read white space from files, now I don't even know what I was expecting it to input!

Thanks for the help and replies! =)