c++ overloading input operator

true_atlantis · 02-24-2004, 06:00 PM

i need to make a HugeInt class that can have up to 30 integers in it, and it can not be negative, i dont know how to overload the input operator... i am thinking i need to know how long the string/number is that is entered...

Code:

istream &operator>> (istream &inStream, HugeInt &obj){
     //need a loop somehow to set each digit to integer[i]
     inStream >> setw(1) >> obj.integer[i];
}

there is a private array of integers which represents each digit of the number, where

HugeInt(1234);

integer[0] = 1
integer[1] = 2
integer[2] = 3
etc.

true_atlantis · 02-24-2004, 06:07 PM

figured it out...

istream & operator>> ( istream &inStream, HugeInt &obj)
{
char *temp;
inStream >> setw(30) >> temp;

obj = temp;

return inStream;
}

wapcaplet · 02-24-2004, 08:51 PM

Another, possibly more robust way, is to use a loop to read in characters until something that isn't a digit is found.

Also, I think you may want to use char temp[30] instead of char *temp, since just using a pointer does not actually allocate any space for characters. I guess the istream >> operator might allocate it, but you can never be too sure

true_atlantis · 02-25-2004, 06:09 PM

in the overloaded = operator, it handles that, so *temp is ok...

wapcaplet · 02-25-2004, 07:24 PM

Actually I was referring to the part where you read stuff in to *temp, before the "obj = temp" statement. Declaring "char *temp" only gives you a pointer; it doesn't actually give you any space to use. I just ran a test program with it, and it looks like it works, but it doesn't seem like the safest way to do it.