Actually, if i dont input a number, the code is entering 3 times in the IF before ask for another input. (and it dont show the first "cout" message)Code:teste: cout << "Nath, digite ate que numero deseja pesquisar por numeros primos.\n"; if(!(cin >> MAX)){ cout << "Erro! Apenas numeros sao validos! (0123456789)\n"; cin.clear(); cin.ignore(); goto teste; return(0); }
Why?
Thanks.
Have you considered using a loop?
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
Why use a loop? My code is supposed to work on this way..
I can't remember, I don't use goto much, but I think
teste:
should be
teste:;
I could be absolutely wrong of course.
The thing people say about goto is that you shouldn't really use it unless there isn't really a viable alternative. Here, as laserlight said, a loop would suffice, so why not just use one?
Questions and Suggestions:
-- Use tabs (or at least spaces)
-- I think that return(0) in the IF statement is useless
-- MAX is an int?
"The Internet treats censorship as damage and routes around it." - John Gilmore
Structured programming.Why use a loop?
Write it as a loop first and post it. If you cannot even do that, you have no business talking about gotos.My code is supposed to work on this way..
Look up a C++ Reference and learn How To Ask Questions The Smart Way
Yes the return is useless, i forgot to get rid of it.
and yes, MAX is an int
Your code is more like assembly...
Goto is quite "deprecated" feature in C++
"The Internet treats censorship as damage and routes around it." - John Gilmore
Incidentally, I do not really see anything wrong about the code (other than the use of an unnecessary goto). I decided to test, and the programs runs as I would expect. Rather strange that you had a problem.
Look up a C++ Reference and learn How To Ask Questions The Smart Way
Code:cout << "Nath, digite ate que numero deseja pesquisar por numeros primos.\n"; while ( !(cin >> MAX) ) { cout << "Erro! Apenas numeros sao validos! (0123456789)\n"; cin.clear(); cin.ignore(); cout << "Nath, digite ate que numero deseja pesquisar por numeros primos.\n"; }
Because this use of goto is bad. There's a maybe a couple of situations where goto makes sense. Other than that it's best if you quickly learn how to use loops.
Anyways, there is an error because if(!(cin >> MAX)) will return false if the user input is valid. That is why the got statement is never read. The if statement returns false.
Originally Posted by brewbuck:
Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.
twomers. your code show the cout message in the while two times if I input one string.
That looks expected. It looks like that is intended to print an error message if the user input is invalid.Anyways, there is an error because if(!(cin >> MAX)) will return false if the user input is valid.
Look up a C++ Reference and learn How To Ask Questions The Smart Way
Yes... just noticed that. my bad.
Originally Posted by brewbuck:
Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.
I thought of saying something about that IF statement, but I was afraid I'm wrong.
"The Internet treats censorship as damage and routes around it." - John Gilmore
