The >> and << thingies..

**eviscerator** · 08-05-2004

Hi, i'm new to this forum. I've been developing applications (mostly games) since the age of 12, but mostly with Click software (www.clickteam.com) which is much easier than programming it (though that's beside the point of this post).

My intent on posting this is that i've been getting into C++ recently, and i'm wondering about the >> and << parts of "cout" and "cin" lines...

for example, if i write this in my code:
cout << "Moo"; - then it has <<

if i need input from the user it's like
cin>>SomeVariable; - and there's the >>

So my question is: Why are they there and what do they mean ? to me they seem pointless compared to Php which is a lot like C++

**prog-bman** · 08-05-2004

They are operators. They are not pointless they make life much easier you'll understand more when you get into c++ a little further.
You could just as well do this

Code:

 cout.write("Hi",2)

but then you would need to specify how much space you are using each time which would not be fun now would it.

**The Dog** · 08-05-2004

It's there to make your life easier. Understand the power of that overloaded operator.

The << and >> are bitwise operators known as the left-shift and right-shift operators.

By overloading these operators, you could have constructs such as the following:

Code:

Foo object;
int ival;
double dval;
 
//..
//..
 
cout << object << " " << ival << " " << dval;

You could write your own classes that overload the << or >> operators , then you could use it with cout, or cin, or even with a file, eg.

Code:

Foo object;
ofstream ofile("test.txt");
ofile << object;

But why were the << and >> used for cin, cout etc?
Well, can you think of a better operator?

**bartybasher** · 08-05-2004

Hi I have used the clickteam tools a lot of my life too. So I probably know where you are coming from with a lot of things regarding C++. So if you ever have any more problems dont hesittate to email me and I will try and explain things in terms of those programs.
(Steiscool from the clickteam forum)

**DougDbug** · 08-05-2004

Every language has it's own syntax, and cin & cout require these operators. This is the simply the way the language is structured and defined by the creators of C/C++. In the C language, input/output has to be done with a function. In C++, you have the option of using overloaded (re-defined) operators.

When used with cin & cout (iostream), these two operators are the insertion (>>) and extraction (<<) operators.

Code:

cout << X ;         // This is C++
cout X ;            // This is an ERROR!
printf("%d", X) ;   // This is C (Also valid in C++)
PRINT X              ' This is BASIC

Don't worry about the fact that these are overloaded operators. (You do need to know that when used with cin and cout, they are NOT the shift-left and shift-right operators.)

About overloading operators -
In C++ you can re-define an operator. (You can even make the + operator subtract!) Normally, you use overloading for something special... For example, you could use the + operator to "add" two images together in a way defined by your program.

**~~Noxir~~** · 08-05-2004

Code:

 cin >> x          // Put in information in X
cout << x                   // Put out information in X

easy? xD

**jlou** · 08-05-2004

Originally Posted by DougDbug

When used with cin & cout (iostream), these two operators are the insertion (>>) and extraction (<<) operators.

There was just a little discussion about this in another thread, and I think you have them switched - inserter (<<) and extractor (>>).

**ryan_germain** · 08-06-2004

Originally Posted by jlou

There was just a little discussion about this in another thread, and I think you have them switched - inserter (<<) and extractor (>>).

doug, jlou is right...i learned the hard way. lol

**The Brain** · 08-06-2004

our book mentions these operators as the >> extraction and << insertion operators. fyi.

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Just accept the syntax!

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