while loop bug or how to fix it?

Question

3.00/5 (2 votes)

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Hello everyone!
Why when i enter an integer it's work perfect(code below), but when i enter a char type simbol it's going crazy and loop run a single line forever? I understand that is a problem with the diferent variable types and compiler do not understand simply what need to enter.
How to define variable, that if you enter a char type, it converts to number and do normaly loop by condition or maybe how to define, that you could enter only a number?

do
{
int x;
std::cout << "Enter number: ";
std::cin >> x;

if (x == 1)
   std::cout "...";
   else if (x == 2)
   std::cout "...";
   else if (x == 3)
   std::cout "...";
   else
   std::cout "...";}
while (x < 1 || x > 3);
{
   x++;
}

Any ideas or offers? :)

Posted 31-Mar-11 7:53am

MNMR

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4 solutions

Solution 5

The problem has been solved. I used string stream.

...
...
do
{
int x;
string xstr;
std::cout << "Enter number: ";
std::getline(std::cin, xstr);
std::stringstream(xstr) >> x;
if (x == 1)
   std::cout "...";
   else if (x == 2)
   std::cout "...";
   else if (x == 3)
   std::cout "...";
   else
   std::cout "...";}
while (x < 1 || x > 3);
{
   x++;
}

And it works now good even you enter a char type. And need don't forget includes...:D

Posted 31-Mar-11 9:48am

MNMR

Solution 4

A similar question had come up before, see this...

why program crashes when user gives char to a integer?[^]

Posted 31-Mar-11 9:34am

Albert Holguin

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Accepted Answer · 2011-03-31T08:18:00

Solution 2

The problem with loop is way too simple.

The problem is the condition and its OR operator (||) you use, Actually your define the union of sets {x < 1} and {x > 3}, which is the set outside of the segment [1, 3]. Should initial value be 3 or more, it will grow infinitely.

Did you really mean AND (&&) operator?

—SA

Posted 31-Mar-11 8:18am

Sergey Alexandrovich Kryukov

Updated 31-Mar-11 8:26am

v3

Comments

Sandeep Mewara 31-Mar-11 14:34pm

5 for the explanation of infinite loop :)

Sergey Alexandrovich Kryukov 31-Mar-11 14:54pm

Thank you, Sandeep.
--SA

Tarun.K.S 31-Mar-11 14:40pm

And a 5 here too! :D
Its been a long time SA, how are you doing sir?

Sergey Alexandrovich Kryukov 31-Mar-11 14:52pm

Thank you, Tarun.
Different...
--SA

Tarun.K.S 31-Mar-11 14:58pm

Ok.

Tarun.K.S 31-Mar-11 14:45pm

Please do vote and accept the answers which helped!

Sergey Alexandrovich Kryukov 31-Mar-11 14:53pm

Yes, I expect you accept this answer.
What condition to use depends not on my advice but on your need.
All you trying to to is to assign x to something. What is should be after the loop?
(Maybe you need just one assignment.) :-)
--SA

Sandeep Mewara · Accepted Answer · 2011-03-31T08:00:00

Solution 1

Possible - using stringstream

Here: Using cin to get user input.[^]
This shows the way to convert the char to integer (a valid value if pssible.)

More details here:Basic Input/Output[^]

UPDATE:
Just came across this too (a good alternative): use std::cin.good() - It is 0 if the input is invalid.

Posted 31-Mar-11 8:00am

Sandeep Mewara

Updated 31-Mar-11 8:01am

v2

Comments

Sergey Alexandrovich Kryukov 31-Mar-11 14:27pm

My 5 but... You did not answer the trivial question about the inf. loop, which is asked in the title.

I did -- please see.
--SA

Tarun.K.S 31-Mar-11 14:39pm

Lol teamwork?!

Sergey Alexandrovich Kryukov 31-Mar-11 14:59pm

A hell of teamwork indeed, of the LOL, too :-)
--SA

Sandeep Mewara 31-Mar-11 14:55pm

Thanks to you too. :)

Sandeep Mewara 31-Mar-11 15:05pm

Great! Good to know.

MNMR 31-Mar-11 14:28pm

Thanks Sandeep Mewara, analyzing now your links.

Tarun.K.S 31-Mar-11 14:45pm

Please do vote and accept the answers which helped!

Tarun.K.S 31-Mar-11 14:40pm

Here comes a 5!

while loop bug or how to fix it?

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while loop bug or how to fix it?

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