I am new to C programming and have been using the GOTO all over the place until today when I was informed it is not preferred practice, and due to its adverse affects on debugging and maintenance should only be used in the rarest of cases.
I can understand that I guess,.
Would an "acceptable" use of GOTO be to rerun the entire main loop? If I make it all the way through my logic, and simply want to start over at the top, would not a simple GOTO back to the top be the best option?
Try to avoid GOTO. Put main loop inside one more loop or try some other logic. Use of GOTO will create all the mess at last.
Would an "acceptable" use of GOTO be to rerun the entire main loop?
No.
If I make it all the way through my logic, and simply want to start over at the top, would not a simple GOTO back to the top be the best option?
Try to think about the real loop control and a better loop construct will come to mind.
---
http://en.wikipedia.org/wiki/Goto#Criticism_of_goto_usage
goto makes the code unreadable and hard to debug. The only place where goto is advisable is coming out of a nested loop.
No.
Try to think about the real loop control and a better loop construct will come to mind.
---
http://en.wikipedia.org/wiki/Goto#Criticism_of_goto_usage
This suggestion intrigues me. Putting my main loop inside another loop. I am not sure I understand how to do it, and it sounds almost more complicated than the problems it might potentially avoid, but if anyone can expand on this thought I would appreciate it.
Again, my limited experience hinders my understanding at this point.
This suggestion intrigues me. Putting my main loop inside another loop. I am not sure I understand how to do it, and it sounds almost more complicated than the problems it might potentially avoid, but if anyone can expand on this thought I would appreciate it.
Again, my limited experience hinders my understanding at this point.
Perhaps if you provide a code snippet on where you think the goto should be used, you may get responses that satisfy your needs.
I'm not totally against the goto, but I haven't used one - well, I can't remember when. Up to about 5 years ago, a language I use on the System i (aka AS400) known as CL had very few good looping constructs (actually none) and your only choice was to use a goto.
Most languages these days (decent ones) provide adequate constructs with regards to sequence, iterations and decisions that would really make you think long and hard as to why you would need to use a goto.
9868 makes a valid observation regarding breaking out of a nested loop, but it would have to be a really deeply nested loop and if that's the case, then it's more than likely a design issue. However, "modern" languages usually provide a "psuedo" goto (e.g. Java with break and a label) for these situations.
Cheers,
JD
This suggestion intrigues me. Putting my main loop inside another loop. I am not sure I understand how to do it, and it sounds almost more complicated than the problems it might potentially avoid, but if anyone can expand on this thought I would appreciate it.
Again, my limited experience hinders my understanding at this point.
In this post, what is it that breaks the loop -- entering an 'n'? How easy is it to spot loop conditions? Might it be easier to tell if it were something like this?
do {
/* show menu */
/* take user input */
/* show result or error */
/* prompt to repeat */
} while ( toupper(cAgain) != 'N' );Here is the type of program I am talking about. It is not a nested loop or anything like that, but once I get to the end, if they user enters Y I would like to send them back to the top and start all over.
I am still not even sure how I would do this with the loop-inside-loop suggestion.
#include <stdio.h> // standard input output library
//defines tax value for calculations
#define DelMar 7.25
#define Encinitas 7.5
#define LaJolla 7.75
char cAgain; //variable for Y/N questions
float user_input() // week 4 addition for sales amount
{ //prompt, collect, and store sale amount
float fAmount; //defines amount type as float
printf("Enter Amount of Sale $ ");
scanf ("%f", &fAmount);
return fAmount;
}
int iMenu() //defines menu variable
{ // menu which prompts, collects, and stores store number
int iSelection; //defines selection type as integer
printf("Tax Calculation for Purchase\n\n"); //changed to reflect week 4 updates
printf("1. Del Mar \n2. Encinitas \n3. La Jolla\n");
printf("\n\nPlease Select Number of Store for Which to Calculate: ");
scanf("%d",&iSelection);
return iSelection;
}
int main() //main loop
{
STARTOVER://start again point
{
float fSales = 0.00; // Sales value for calculations
int iStorenum; //defines store for main loop, menu will not work without
fSales = user_input(); //new week 4 loop for sales total
while (fSales <0.0) //new week 4 loop to validate sales amount
{
printf("SALE AMOUNT CANNOT BE LESS THAN $0.00. Re-Enter: $ ");
{
scanf ("%f",&fSales); // scans new input for validity
}
} // ends while loop
iStorenum = iMenu(); //displays menu created above
while (iStorenum <1 || iStorenum >3) //if store number is not 1, 2 or 3
{
printf("INVALID NUMBER ENTERED! Please enter 1,2 or 3: ");
{
scanf("%d", &iStorenum); //scans input at INVALID prompt
}
} // end while loop
if (iStorenum == 1)
//Calculates and Displays Del Mar Store, Sales, Tax rate, and Tax
printf("\nDel Mar \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",fSales, DelMar, fSales*DelMar/100, DelMar*fSales/100+fSales);
if (iStorenum == 2)
//Calculates and Displays Encinitas Store, Sales, Tax rate, and Tax
printf("\nEncinitas \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",fSales, Encinitas, fSales*Encinitas/100, Encinitas*fSales/100+fSales);
if (iStorenum == 3)
//Calculates and Displays La Jolla Store, Sales, Tax rate, and Tax
printf("\nLa Jolla \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",fSales, LaJolla, fSales*LaJolla/100, LaJolla*fSales/100+fSales);
printf("\n\tWould you like to calculate for another store? (y/n) ");//prompts for repeat
scanf("%c", &cAgain);//scans input at store number prompt
if (cAgain == 'y'|| cAgain == 'Y')//repeats calculator
{
goto STARTOVER; //back to top
}
else if (cAgain == 'n' || cAgain == 'N')//end
return 0; // successful loop end
}
}You would use a do-while loop. Essentially you'll keep asking for user input in the body of the do loop while the user keeps answering 'y' or 'Y' for more calculations.
int main() //main loop
{
do {
float fSales = 0.00; // Sales value for calculations
int iStorenum; //defines store for main loop, menu will not work without
fSales = user_input(); //new week 4 loop for sales total
while (fSales < 0.0) //new week 4 loop to validate sales amount
{
printf("SALE AMOUNT CANNOT BE LESS THAN $0.00. Re-Enter: $ ");
{
scanf("%f", &fSales); // scans new input for validity
}
} // ends while loop
iStorenum = iMenu(); //displays menu created above
while (iStorenum < 1 || iStorenum > 3) //if store number is not 1, 2 or 3
{
printf("INVALID NUMBER ENTERED! Please enter 1,2 or 3: ");
{
scanf("%d", &iStorenum); //scans input at INVALID prompt
}
} // end while loop
if (iStorenum == 1)
//Calculates and Displays Del Mar Store, Sales, Tax rate, and Tax
printf(
"\nDel Mar \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",
fSales, DelMar, fSales * DelMar / 100, DelMar * fSales
/ 100 + fSales);
if (iStorenum == 2)
//Calculates and Displays Encinitas Store, Sales, Tax rate, and Tax
printf(
"\nEncinitas \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",
fSales, Encinitas, fSales * Encinitas / 100, Encinitas
* fSales / 100 + fSales);
if (iStorenum == 3)
//Calculates and Displays La Jolla Store, Sales, Tax rate, and Tax
printf(
"\nLa Jolla \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",
fSales, LaJolla, fSales * LaJolla / 100, LaJolla * fSales
/ 100 + fSales);
printf("\n\tWould you like to calculate for another store? (y/n) ");//prompts for repeat
scanf("%c", &cAgain);//scans input at store number prompt
} while (cAgain == 'y' || cAgain == 'Y');
return 0;
}By the way, your code doesn't work quite right at the moment as it only prompts for one set of input data. When prompting for the answer to more calculations, the scanf will pick up the '\n' character from the previous scanf of the store number. You'll have to "consume" that character from the input buffer before prompting for character input.
Thanks Yellow Snow, I am going to give that a try.
Can you help me on something stupid real quick? I have two copies of my code saved, one works and one does not (as you pointed out). For the life of me I cannot see the difference.
Can you look as this working version and tell me what is different?
I have gone through line by line and both versions look identical to me.
#include <stdio.h> // standard input output library
//defines tax value for calculations
#define DelMar 7.25
#define Encinitas 7.5
#define LaJolla 7.75
char cAgain; //variable for Y/N questions
float user_input() // week 4 addition for sales amount
{ //prompt, collect, and store sale amount
float fAmount; //defines amount type as float
printf("Enter Amount of Sale $ ");
scanf ("%f", &fAmount);
return fAmount;
}
int iMenu() //defines menu variable
{ // menu which prompts, collects, and stores store number
int iSelection; //defines selection type as integer
printf("Tax Calculation for Purchase\n\n"); //changed to reflect week 4 updates
printf("1. Del Mar \n2. Encinitas \n3. La Jolla\n");
printf("\n\nPlease Select Number of Store for Which to Calculate: ");
scanf("%d",&iSelection);
return iSelection;
}
int main() //main loop
{
STARTOVER://start again point
{
float fSales = 0.00; // Sales value for calculations
int iStorenum; //defines store for main loop, menu will not work without
fSales = user_input(); //new week 4 loop for sales total
while (fSales <0.0) //new week 4 loop to validate sales amount
{
printf("SALE AMOUNT CANNOT BE LESS THAN $0.00. Re-Enter: $ ");
{
scanf ("%f",&fSales); // scans new input for validity
}
} // ends while loop
iStorenum = iMenu(); //displays menu created above
while (iStorenum <1 || iStorenum >3) //if store number is not 1, 2 or 3
{
printf("INVALID NUMBER ENTERED! Please enter 1,2 or 3: ");
{
scanf("%d", &iStorenum); //scans input at INVALID prompt
}
} // end while loop
if (iStorenum == 1)
//Calculates and Displays Del Mar Store, Sales, Tax rate, and Tax
printf("\nDel Mar \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",fSales, DelMar, fSales*DelMar/100, DelMar*fSales/100+fSales);
if (iStorenum == 2)
//Calculates and Displays Encinitas Store, Sales, Tax rate, and Tax
printf("\nEncinitas \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",fSales, Encinitas, fSales*Encinitas/100, Encinitas*fSales/100+fSales);
if (iStorenum == 3)
//Calculates and Displays La Jolla Store, Sales, Tax rate, and Tax
printf("\nLa Jolla \tSale $%.2f\tRate %.2f%%\tTax $%.2f%\tTotal= \t$%.2f\t\n\n",fSales, LaJolla, fSales*LaJolla/100, LaJolla*fSales/100+fSales);
printf("\n\tRun Calculator Again? (y/n) ");//prompts for repeat
scanf("%c", &cAgain);//scans input at store number prompt
if (cAgain == 'y'|| cAgain == 'Y')//repeats calculator
{
goto STARTOVER; //back to top
}
else if (cAgain == 'n' || cAgain == 'N')//end
return 0; // successful loop end
}
}Rather than "eye balling" the two files and trying to detect the differences, use a file compare utility that is provided with your OS e.g. fc on Windows or diff on Linux/Unix.
never knew such a thing existed. I will give it a try.
Thanks again for all your help.
Thanks for you all, now i noe how to use GOTO liao...
haha^^
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