Thread: Variable Type Problems

I know that this question has been answered before but I have searched all over and not found what I'm looking for. I'm writing a console application. We all know how much the computer hates it when you input a character when you should have inputted some type of number. I would like to know how to avoid this... Example

Code:

...
int I;

cin>>I;

if (A character was put in){
    start over
}
else {
    Its all good
}

I'm sure someone else has asked this before but I searched for a long time and didn't find what I was looking for... Thanks for your help!

There is a funciton called isalpha() that may be what you are looking for.

Code:

do
{
c=getch();
}while( ! isalpha(c) )

I still don't understand...
In your example, of what variable type is "c".
And, I'm not sure if this matters, but I'm using "cin" not getch();

Well, fgets() has always worked for me

Why not try this:

Code:

int iget(int max_buff = 100) {
 char buff[max_buff ];
 return atoi(fgets(buff, max_buff , stdin));
}



int main() {

int num;

do{

  num = iget();

  if(num != 0) //...user pressed enter, but inputted nothing...
  break;

}while(1);

return 0;
}

So what you are saying is that there is no possible way to avoid this problem using std::cin? I don't get the other examples, I just finished learning the basics of the language.

Of course you can over-ride cin, but I haven't tried that yet...but look:

Code:

class my_cin {
public:

char buffer[10000];

int operator >> (int num) {
  return num = atoi(fgets(buffer, 10000, stdin));  
 }
float operator >> (float num) {
  return num = atof(fgets(buffer, 10000, stdin));  
 }
long operator >> (long num) {
  return num = atol(fgets(buffer, 10000, stdin));  
 }
double operator >> (double num) {
  return num = atod(fgets(buffer, 10000, stdin));  
 }
char operator >> (char c) {
 return   c = getch();
 }
char * operator >> (char str[]) {
 return fgets(str, 10000, stdin);  
 }
char * get( char str[], int max ) {
 return fgets(str, max, stdin);
}
};

Now declare a global input object (like cin)...


my_cin inn;



int main() {

char c;
int i;
double d;
char string[100];

inn >> string;

inn >> d;

//...or even:

char ch = inn >> c; //...get c, and also assign value to ch.

return 0;
}

Originally posted by Sebastiani

Why not try this:

Code:

int iget(int max_buff = 100) {
 char buff[max_buff ];
 return atoi(fgets(buff, max_buff , stdin));
}

Because it won't work.
The size of arrays have to be constant

Use elad's method with a little modification: Add ignore(10000) after cin.clear().

But if you're looking for a complete function, try this:
It won't decrease functionality of cin like declaring a new class will.
(custom classes might override istream::operator>>)

Code:

//nice, safe reading function
template<typename T> bool get(T& t)
{
    using std::cin;
    cin>>t;
    if (cin.eof())
        cin.clear();
    else if (cin.fail())
    {
        cin.clear(); 
        cin.ignore(std::numeric_limits<std::streamsize>::max(),'\n');    
    }
    else if (cin.bad())
        cin.clear();
    else
    {
        cin.ignore(std::numeric_limits<std::streamsize>::max(),'\n'); 
        return true;
    }
    return false;
}

Very good point Sang-Drax. Only poeple like me who hate the STL should be writing their own input classes

But very good code example...