Going Back To The Start OF C++.

[Sunny123]

hello,

i am usung the following code in C++

std::cout<<"\nDo You Want To Solve Another Quadratic
Equation?\nYes(y==Y) No(n==N): ";
fflush(stdin); // flush input buffer
int sel = tolower(getchar());
while(sel != 'y' && sel != 'n')
{
std::cout<<"\nEither Choose \"y or Y\" For \"YES\" OR \"n or N\"
For \"NO\": "<<std::endl;
fflush(stdin); // flush input buffer
sel = tolower(getchar());
}
if(sel == 'y')
{
system("cls");
goto Start;
}
else
return 0;
}

to clear the program and go back to the start of it.

i.e. once you have worked out one quadratic it gives you the option
whether to do another or quit.

is there a better way of writing this code, because my teacher says
that i should not use fflush(stdin);

thanks

 

[Sunny123]

sorry for the repost,

if there is not another code that will do the same thing, can i make
this code any better.

thanks

 

[Githlar]

To flush the input buffer C++ style use this while loop:

while(std::cin.get() != '\n');

To flush the output buffer however, you can use std::cout.flush().

Githlar

 

[Daniel T.]

hello,

i am usung the following code in C++

std::cout<<"\nDo You Want To Solve Another Quadratic
Equation?\nYes(y==Y) No(n==N): ";
fflush(stdin); // flush input buffer
int sel = tolower(getchar());
while(sel != 'y' && sel != 'n')
{
std::cout<<"\nEither Choose \"y or Y\" For \"YES\" OR \"n or N\"
For \"NO\": "<<std::endl;
fflush(stdin); // flush input buffer
sel = tolower(getchar());
}
if(sel == 'y')
{
system("cls");
goto Start;
}
else
return 0;
}

to clear the program and go back to the start of it.

i.e. once you have worked out one quadratic it gives you the option
whether to do another or quit.

is there a better way of writing this code, because my teacher says
that i should not use fflush(stdin);

What were his reasons? If he doesn't want you to mix C IO usage and C++
IO usage, then I suggest looking into how to use 'cin' and istreams.

I can't help but wonder what he thinks about the goto, but I don't want
to start a flame war so maybe I should delete this sentence...

 

[Sunny123]

What were his reasons? If he doesn't want you to mix C IO usage and C++
IO usage, then I suggest looking into how to use 'cin' and istreams.

I can't help but wonder what he thinks about the goto, but I don't want
to start a flame war so maybe I should delete this sentence...

"I can't help but wonder what he thinks about the goto, but I don't
want
to start a flame war so maybe I should delete this sentence... "

yeah he was saying that this was not a good thing to do.

any ideas would be much appreciated.

 

[Ron Natalie]

What were his reasons? If he doesn't want you to mix C IO usage and C++
IO usage, then I suggest looking into how to use 'cin' and istreams.

How about the fact that it's undefined behavior. Fflush only does
something on output streams (or streams not being used for input).
Calling fflush in stdin is UNDEFINED BEHAVIOR.

 

[Sunny123]

could someone tell me what each line in the code is

1cout << "\nDoYouWantoSolveAnotherQuadratic Equation?\nYes(y==Y)
No(n==N): ";
2 while(cin.get() != '\n');
3 int ch = tolower(getchar());
4 while(ch != 'y' && ch != 'n')
5 {
6cout << "\nEither Choose \"y or Y\" For \"YES\" OR \"n or N\" For
\"NO\": " << endl;
7 while(cin.get() != '\n');
8 ch = tolower(getchar());
9 }
10 if(ch == 'y')
11 {
12 system("cls");
13 goto Start;
14 }
15 else
16 return 0;
17 }


it is mainly lines 2 and 3, and lines 7 and 8

 

[Sunny123]

could someone tell me what each line in the code is

1cout << "\nDoYouWantoSolveAnotherQuadratic Equation?\nYes(y==Y)
No(n==N): ";
2 while(cin.get() != '\n');
3 int ch = tolower(getchar());
4 while(ch != 'y' && ch != 'n')
5 {
6cout << "\nEither Choose \"y or Y\" For \"YES\" OR \"n or N\" For
\"NO\": " << endl;
7 while(cin.get() != '\n');
8 ch = tolower(getchar());
9 }
10 if(ch == 'y')
11 {
12 system("cls");
13 goto Start;
14 }
15 else
16 return 0;
17 }


it is mainly lines 2 and 3, and lines 7 and 8.

thanks

 

[REH]

To flush the input buffer C++ style use this while loop:

while(std::cin.get() != '\n');

To flush the output buffer however, you can use std::cout.flush().

Githlar

What is wrong with:

std::cin.sync();

REH