Thread: Unknown error with Y/N type system.

For school (voluntary, not a required project), I'm creating a bonuscalc for the teachers to use. Everything is coming along smoothly, except for a portion of code that handles whether or not a file is present.

The function is called 'isFoundDb' and is of type 'int'. It returns a value to main depending on whether or not the file is found, and whether or not the user chooses to use the default values in the absence of that file. If the file is found, return 1. If not found, AND the user chooses not to use the file (which is a sort of database), return 0. If the user wants to use the file, return -1.

The program is split up into one file per function. 'Main.c' includes 'isFoundDb.c' and the .h file holding all the functions I have prototyped. Therefore, each .c file defines the functions in the .h file.


isFoundDb.c:

Code:

#include <stdio.h>
#include <conio.h>
#include "bonusCalc.h"

int isFoundDb() {

char choice = -1;
int cdn = -2;
int i = 0;

FILE *database;
database = fopen("DATABASE.TXT","r");

if (database == NULL) {
 printf("WARNING: \n");
 printf("Database file not found!\n");
 printf("Did you copy over the BIN folder?\n");
 printf("Default bonuses will be used.\n");

do {
   printf("Is that okay? (y/n): ");
   fflush(stdin);
   choice = getch();

   switch(tolower(choice)) {
   case 'y': 
   cdn = 0;
   break;
   case 'n': 
   cdn = -1;
   break;
   default: printf("That isn't a valid choice\n");
   }

   if (cdn >= 0) {
   i = 1;
   }
   else {
   i = 0;
   }
   } while (i = 0);
}

else if (database != NULL) {
 cdn = 1;
}
else {
 cdn = -2;
 }
 
return cdn;
}

Main.c:

Code:

#include <stdio.h>
#include "bonusCalc.h"
#include "isFoundDb.c"
int main(int argc, char *argv[]) {
int done = 0; /* Ensure that the following process isn't complete */
int quit = 0; /* Should the program quit? */
/* Check to make sure database.txt is present in the Bin folder
* If isFoundDb returns 0, don't use db
* If isFoundDb returns 1, use db
* If isFoundDb returns -1, the file is missing and the user must locate the file */
do {
if (isFoundDb() == 0) {
 printf("\nUsing default values!\n");
 done = 1;
 }
else if (isFoundDb() == 1) {
 printf("\nUsing database values!\n");
 done = 1;
 }
else if (isFoundDb() == -1) {
 printf("\nDatabase.txt missing!\n");
 quit = 1;
 done = 1;
 }
else {
 printf("Unknown error!\n");
 }
} while (done != 1);
return 0;
}

BonusCalc.h:

Code:

#ifndef bonusCalc_h
#define bonusCalc_h
int isFoundDb();
#endif

The code works perfectly except for when the user types 'n' in which case it repeats from the if (database == NULL) portion of code... which I don't understand. I'd have thought it would repeat from the embedded do while loop for some obscure reason. But what is perplexing is that if the user types 'y' it works fine. I'm at a loss.

Any help would be appreciated

PS: I tried using goto and even removing the do while loop but nothing's working.

First indent your code.

Second, never use goto, since it produces spaghetti code, which is not readable, thus can not be maintained.

Third, welcome to the forum

Last, but not least,

Code:

while (i = 0);

You have forgotten an equal sign in line 34.

Well, goto is considered to be by most of us not good. I could explain, but I am sure you will find enough info in google

I think you didn't see my edited post

Originally Posted by JoshLalonde

And regarding goto, meh. It has its benefits, depends. Like, a quick way to exit a program in the case of an error...

If you just want to exit in the case of an error, you should use exit(). As a slightly more flexible alternative, define a function called "fatal" that each of your functions will call if a fatal error happens. This function should just print an error message and then exit. This has the advantage that you can extend the function to do other things as your needs increase, like print a stacktrace when it is in debugging mode, for example.

Another comment on your code - you are using fflush(stdin) which is probably causing a problem. What are you trying to do with that call?

Ok, let's see the main now.

How many times will your function isFoundDB will be executed?

Originally Posted by JoshLalonde

I heard you're supposed to flush the buffer before running getch();

No. Using fflush does not work on input streams. If you want to read one line of input, normally we use fgets. Also, if you indent your code you will notice another problem: at the top you do

Code:

if (database == NULL) {
...
} else if (database != NULL) {
...
} else {
...
}

The last part does not do anything because database can only be NULL or not NULL, there is no third possibility. One more thing. You are using cdn as your return value for this function. That means you can just return this value immediately once you set it. In other words, don't say cdn = 1. Just return 1.

Your loop is really going to last forever until you return a valid value 0 or -1. So, in this case we write either while(1) ... or for ( ; ; )

Finally you need to close the file if you opened it successfully.

The modified function is below

Code:

int isFoundDb(void) {
 
	char choice = -1;
	 
	FILE *database;
	database = fopen("DATABASE.TXT","r");
	 
	if (database == NULL) {
		printf("WARNING: \n");
		printf("Database file not found!\n");
		printf("Did you copy over the BIN folder?\n");
		printf("Default bonuses will be used.\n");

		while (1) {
			printf("Is that okay? (y/n): ");
			char buf[1000];
			fgets(buf, sizeof(buf), stdin);
			choice = buf[0];

			switch(tolower(choice)) {
				case 'y': 
				return 0;
				break;
				case 'n': 
				return -1;
				break;
				default: printf("That isn't a valid choice\n");
			}
		}
	}
	fclose(database);
	return 1;
}

Thank you so very much for your help I knew there was something wrong with the loop, but I couldn't quite figure that out. And oh, lol. Thanks again, guys! I haven't checked it yet, but I'm going to assume what you've given me will work. So leave this open until I edit my post, thanks

EDIT: Still not working!
Below is a screenshot of running it in cmd.exe.

EDIT2: I just realized the code you gave me is missing the else { }. Technically I guess it's not necessary, but I'm going to try to incorporate it to see if that helps.

EDIT3: Wait, so the reason I assigned a 'cdn' variable was because of this. If for some odd reason the code ends up at the end of the function and it doesn't return anything, that's a problem... This code assumes that all the if/else stuff works. Even then, adding an else{} portion didn't help. Still repeats for some reason... Mayhaps it could be the compiler? I already discovered that the conio.h file was erroneous and could not be usei



Here is the changes I made:

Code:

#include <stdio.h>
#include "Bonuscalc.h"


int isFoundDb() {
 
    char choice = -1;
    int cdn = -3;
     
    FILE *database;
    database = fopen("DATABASE.TXT","r");
     
    if (database == NULL) {
        printf("WARNING: \n");
        printf("Database file not found!\n");
        printf("Did you copy over the BIN folder?\n");
        printf("Default bonuses will be used.\n");


        while (1) {
            printf("Is that okay? (y/n): ");
            char buf[1000];
            fgets(buf, sizeof(buf), stdin);
            choice = buf[0];


            switch(tolower(choice)) {
                case 'y': 
                cdn = 0;
                break;
                case 'n': 
                cdn = -1;
                break;
                default: printf("That isn't a valid choice\n");
            }
            break;
        }
        
    }
    else {
        fclose(database);
        cdn = 1;
    }
    return cdn;
}

I'm aware that this breaks the repeated loop in case they don't enter N/n or Y/y. But that's a quick fix. I'm more concerned on why it repeats the IF/ELSE statement over again.

Sorry for the double post, but it's for emphasis. I determined that there's a problem with the if/else in isFoundDb. I created a test file removing the embedded loops and it repeats infinitely. The only thing preventing it last time was the loops jumping to the end of the function.

EDIT: Problem was with main.c and using a do while loop that wasn't supposed to be there. But now that the embedded loops are gone, it still repeats 3 times. (Essentially I forced it to act as if the user typed n).

GRRRR Tested with GCC and didn't work either.

Oh, so that's what the problem is. I should store the return value of isFoundDb into a variable and then check the variable rather than running the function each time and determining its return. Right? Also, since there's no other condition on which isFoundDb will quit. Just have two ifs, and the last else will be 'not found'.

EUREKA! That's what it was. Fix was to store return value into a variable.
Thanks for teaching me this important lesson about how C works, all of you

You can close this thread now

Εύρηκα! you said and you are right Bravo.

Don't worry about the status of the thread