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Basic Input/Output Tutorial

dharden (2)
The Basic Input/Output Tutorial found here:

http://www.cplusplus.com/doc/tutorial/basic_io/

contains this:

---------------

cin >> a;
cin >> b;


....the user is expected to introduce two values, one for variable a, and another for variable b. Any kind of space is used to separate two consecutive input operations; this may either be a space, a tab, or a new-line character.

---------------

This is wrong, isn't it? two consecutive input operations don't always need to be separated by whitespace...right?

George P (5611)
Without whitespace how many variables can 1234 fill?

How many for 12 34?
George P (5611)
Let's compile some real simple code and see why whitespace is needed to differentiate inputs:

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#include <iostream>

int main()
{
   int a { };
   std::cin >> a;

   int b { };
   std::cin >> b;

   std::cout << a << ", " << b << '\n';
}


When run enter each value separate, followed by hitting the return key (the return key enters a newline into the input stream....whitespace):
12
34
12, 34


Separate the values by a space, then enter:
12 34
12, 34

A space is whitespace

tab and enter:
12      34
12, 34

tab is whitespace

Only a comma, no other whitespace, and enter:
12,34
12, 0

Hmmmm, maybe just a comma alone isn't a good way to separate out multiple inputs.

No whitespace, and just hit enter:
1234

The program only received one value, 1234, and is waiting for another to be entered.
lastchance (6980)
Whitespace isn't always needed.

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#include <iostream>
#include <sstream>
using namespace std;

int main()
{
   int a;
   char b;

   stringstream anInputStream( "12x" );
   anInputStream >> a >> b;

   cout << "a is " << a << '\n';
   cout << "b is " << b << '\n';
}
 
a is 12
b is x



Not very pretty, but you could also try, for two integers:
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#include <iostream>
#include <sstream>
using namespace std;

int main()
{
   int a, b;

   stringstream anInputStream( "1234-5678" );
   anInputStream >> a >> b;

   cout << "a is " << a << '\n';
   cout << "b is " << b << '\n';
}
 
a is 1234
b is -5678



And this one is just an encouragement to make mistakes!
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#include <iostream>
#include <sstream>
using namespace std;

int main()
{
   int a;
   double b;

   stringstream anInputStream( "1234.5678" );
   anInputStream >> a >> b;

   cout << "a is " << a << '\n';
   cout << "b is " << b << '\n';
}
 
a is 1234
b is 0.5678




For non-numeric input:
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#include <iostream>
#include <sstream>
using namespace std;

int main()
{
   char a, b, c;
   
   stringstream anInputStream( "c++" );
   anInputStream >> a >> b >> c;

   cout << "a is " << a << '\n';
   cout << "b is " << b << '\n';
   cout << "c is " << c << '\n';

a is c
b is +
c is +
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