Validation in C

[moogle1979]

I try to validate a user response to weed out characters by repeating the loop and use only integers

I either get no validation or it validates but repeats everything and misses the if's I set up for the integers I am looking for

Here is what I have so far:



int main() //starts program
{
//Declare Variables
float taxdelmar, taxencinitas, taxlajolla;//declaring tax variables
float fCost, fCheck;//calculation operator
int iChoice; //variable for store choice
int iValid, iStore, iResponse, iCont, iCon, iName; //variable for validity check
char cRepeat, cCheck, cStore; //variable for program repeat


//Variable Defined
fCost = 0; //defined for subtotal
fCheck = 0; //defined for validity check
cRepeat = '\0'; //defined for program repeat
iValid = 2; //defined validity for store chosen
iResponse = 0;
iChoice = 0; //defined choice for store
iStore = 2; //defined for subtotal validity
iCont = 1;
iCon = 0;
iName = 0;
cStore = '\0';

//Tax rates defined
taxdelmar=.0725; //tax rate for Del mar 7.25%
taxencinitas=.0750; //tax rate for Encinitas 7.50%
taxlajolla=.07750; //tax rate for La Jolla 7.75%

STORES:

//User Requirements
printf("\n\tWelcome to Kudler Fine Foods\n\n\tWe hope you enjoyed your shopping experience.\n"); //Welcome message
printf("\n\t1. Del Mar\n");
printf("\n\t2. Encinitas\n");
printf("\n\t3. La Jolla\n");
printf("\n Please choose your Location (1,2, or 3): ");
scanf ("%d", cStore);
iChoice = isdigit(cStore);
if(iChoice ==1)
{
printf("\n Welcome Del Mar Associate.\n");
printf(" Please enter your sub-total: $");
scanf("\n%f", &fCost);//sale sub-total
printf(" --------------------------------\n");
printf(" Your total tax is $%.2f\n", fCost * .0725);//in-line calculation
printf(" The total amount owed is $%.2f\n", fCost * (1+.0725));//in-line calculation
goto REPEAT;
}
else if(iChoice ==2)
{
printf("\n Welcome Encinitas associate.\n");
printf(" Please enter your sub-total: $");
scanf("%f", &fCost);//sale sub-total
printf(" --------------------------------\n");
printf(" Your total tax is $%.2f\n", fCost * .075);//in-line calculation
printf(" The total amount owed is $%.2f\n", fCost * (1+.075));//in-line calculation
goto REPEAT;
}
else if(iChoice ==3)
{
printf("\n Welcome La Jolla associate.\n");
printf(" Please enter your sub-total: $");
scanf("%f", &fCost);//sale sub-total
printf(" --------------------------------\n");
printf(" Your total tax is $%.2f\n", fCost * .0775);//in-line calculation
printf(" The total amount owed is $%.2f\n", fCost * (1+.0775));//in-line calculation
goto REPEAT;
}
else
{
fflush(stdin);
goto STORES;
}
REPEAT:
getchar();//keeps application viewable on screen
// end selection
return 0;
}

[dwhitney67]

I have not seen such bad code since the days where BASIC was en vogue.

What's with the goto statements? There are other tools available to repeat code (e.g. while- or for-loops).

With modern C compilers it is possible to declare and initialize a variable in one statement. For instance:

int value = 0;

Pay attention to your scanf() function (the first one where you get cStore)... you forgot to provide the address of the variable where you want the data stored. Also, why are you reading a digit as a character?

Anyhow, I hope you are not referencing a C programming book written 20 years ago. Here's how I would have written the program. If you have any questions, feel free to ask them!

To compile the code:

gcc -Wall -pedantic -std=c99 store.c -o store

#include <stdio.h> //for printf(), scanf()
#include <string.h> //for strcpy()


int main() //starts program
{
int storeID = 0;
char storeLocation[50] = {0};
float taxRate = 0.0;
float subTotal = 0.0;

//Tax rates defined
const float taxDelMar = 0.0725; //tax rate for Del Mar 7.25%
const float taxEncinitas = 0.0750; //tax rate for Encinitas 7.50%
const float taxLaJolla = 0.07750; //tax rate for La Jolla 7.75%

do
{
//User Requirements
printf("\n\tWelcome to Kudler Fine Foods\n\n\t"
"We hope you enjoyed your shopping experience.\n"); //Welcome message

printf("\n\t1. Del Mar\n");
printf("\n\t2. Encinitas\n");
printf("\n\t3. La Jolla\n");
printf("\n Please choose your Store Location (1, 2, or 3): ");

scanf("%d", &storeID);

switch (storeID)
{
case 1:
strcpy( storeLocation, "Del Mar" );
taxRate = taxDelMar;
break;

case 2:
strcpy( storeLocation, "Encinitas" );
taxRate = taxEncinitas;
break;

case 3:
strcpy( storeLocation, "La Jolla" );
taxRate = taxLaJolla;
break;

default:
printf( "Error... Invalid Store ID given!\n" );
break;
}
} while ( taxRate == 0.0 );

printf("\nWelcome %s associate.\n", storeLocation);
printf("Please enter your sub-total: $");
scanf("%f", &subTotal); //sale sub-total

printf("--------------------------------\n");
printf("Subtotal............ $%.2f\n", subTotal);
printf("Total tax........... $%.2f\n", subTotal * taxRate);
printf("Total amount due.... $%.2f\n", subTotal * (1+taxRate));

return 0;
}

[Can+~]

"La Jolla" shouldn't be "La Joya"?

(Spanish speaker here)

[dwhitney67]

"La Jolla" shouldn't be "La Joya"?

(Spanish speaker here)

No he and California are correct!

La Jolla = The Jewel (?)
La Jolla, California... sits just north of San Diego. You can read all about it here: http://en.wikipedia.org/wiki/La_Jolla

[moogle1979]

I only added the goto's until I got the Store number validation down then I was going to take them out and work on the total and tax area

[moogle1979]

That is a lot cleaner of a code you wrote but it still has the validation issue that I have been trying to solve

if someone accidentally types in 3e or decides to be play like they cannot follow the instructions then you have the unending loop that I have been trying to find a way to prevent

[Tony Flury]

The issue is i think that scanf("%d",....) does something you may not expect if the value entered is not exactly the format expected - in this case scanf expects only numeric charatcers with a terminating whitespace or newline - if the user enters "3e" i think that scanf ignores it, and continues to wait for a real integer.

if you need to validate the data, then you need read it as single characters (or as a string), and make sure that the user only entered digit characters - see isdigit(char c) - and then when you know that the data the user has entered is numeric only - then convert it to a number using something like atoi()

Hope this helps.

[moogle1979]

Thanks Tony, I had been looking into isdigit (char c) just did not know exactly how to go about it.

[Tony Flury]

i wont post the C code here - i am sure to get the syntax wrong.

what you need to do is get characters one at a time - and check it is a digit.

It does depends on what exact input you want to accept :

for instance :
is " 3" - leading space - valid or invalid ?
is "e3" - leading non-digit - valid (value 3) or invalid ?
is "3e" - trailing non-digits - valid (value 3) or invalid ?

and there are possible some other cases you need to think about

you need probably at least two loops though
1st to strip off any invalid leading characters
2nd to read in valid digits until an invalid character or whitesapce is found

and then if you have a valid input - use atoi to convert the string into a number ;

[dwhitney67]

i wont post the C code here - i am sure to get the syntax wrong.

what you need to do is get characters one at a time - and check it is a digit.

It does depends on what exact input you want to accept :

for instance :
is " 3" - leading space - valid or invalid ?
is "e3" - leading non-digit - valid (value 3) or invalid ?
is "3e" - trailing non-digits - valid (value 3) or invalid ?

and there are possible some other cases you need to think about

you need probably at least two loops though
1st to strip off any invalid leading characters
2nd to read in valid digits until an invalid character or whitesapce is found

and then if you have a valid input - use atoi to convert the string into a number ;

EDITED: I got semi-bored and developed a function that will query and check for a valid store ID, as per the OP's requirements:


#include <stdio.h>
#include <string.h>

#define isdigit(c) ((((c) - '0') >= 0) && (((c) - '0') <= 9))
#define inrange(c,l,h) ((((c) - '0') >= (l)) && (((c) - '0') <= (h)))

int getStoreID()
{
int storeID = 0;

do
{
printf("Enter Store Number [1, 2, 3]: ");

char str[3] = {0};
scanf("%2s", str);

if ( (strlen(str) > 1) ||
(!isdigit(str[0]) || !inrange(str[0], 1, 3)) )
{
while (getchar() != 0xa);
printf("Bad input... try again fool!\n");
continue;
}

storeID = str[0] - '0';
break;

} while(1);

return storeID;
}

int main()
{
printf( "Store ID = %d\n", getStoreID() );
return 0;
}

[dwhitney67]

The full code:

#include <stdio.h> //for printf(), scanf()
#include <string.h> //for strcpy()


#define isdigit(c) ((((c) - '0') >= 0) && (((c) - '0') <= 9))
#define inrange(c,l,h) ((((c) - '0') >= (l)) && (((c) - '0') <= (h)))

int getStoreID()
{
int storeID = 0;

printf("\n\tWelcome to Kudler Fine Foods\n\n\t"
"We hope you enjoyed your shopping experience.\n"); //Welcome message

printf("\n\t1. Del Mar\n");
printf("\n\t2. Encinitas\n");
printf("\n\t3. La Jolla\n");

do
{
printf("\nPlease choose your Store Location (1, 2, or 3): ");

char str[3] = {0};
scanf("%2s", str);

if ( (strlen(str) > 1) ||
(!isdigit(str[0]) || !inrange(str[0], 1, 3)) )
{
while (getchar() != 0xa);
printf("Bad input... try again fool!\n");
continue;
}

storeID = str[0] - '0';
break;

} while(1);

return storeID;
}


int main() //starts program
{
int storeID = 0;
char storeLocation[50] = {0};;
float taxRate = 0.0;
float subTotal = 0.0;

//Tax rates defined
const float taxDelMar = 0.0725; //tax rate for Del Mar 7.25%
const float taxEncinitas = 0.0750; //tax rate for Encinitas 7.50%
const float taxLaJolla = 0.07750; //tax rate for La Jolla 7.75%

do
{
//User Requirements
storeID = getStoreID();

switch (storeID)
{
case 1:
strcpy(storeLocation, "Del Mar");
taxRate = taxDelMar;
break;

case 2:
strcpy(storeLocation, "Encinitas");
taxRate = taxEncinitas;
break;

case 3:
strcpy(storeLocation, "La Jolla");
taxRate = taxLaJolla;
break;

default:
printf("Error... Invalid Store ID given!\n");
break;
}
} while (taxRate == 0.0);

printf("\nWelcome %s associate.\n", storeLocation);
printf("Please enter your sub-total: $");
scanf("%f", &subTotal); //sale sub-total

printf("--------------------------------\n");
printf("Subtotal............ $%.2f\n", subTotal);
printf("Total tax........... $%.2f\n", subTotal * taxRate);
printf("Total amount due.... $%.2f\n", subTotal * (1+taxRate));

return 0;
}