CODEWITHSUNDEEP
c++
Francesco Bonizzi
Francesco Bonizzi

Reputation: 5302

About return in C++

Sorry for this newbie question, but I can't find on google what I need to know.

I understand return, but don't understand this... What does it mean this?

  return (tail+1)%N == head%N;

Thanks a lot for patience.

Upvotes: 3

Views: 175

Answers (6)

Kragh
Kragh

Reputation: 403

it returns true if remainder of the division for tail + 1 and head is the same

for example if tail is 2, head is 1 and N is 2

(tail + 1) % N is 1

head % N is 1 too

so whole expression returns true

Upvotes: 2

Toby
Toby

Reputation: 3905

Short Answer:

Because of the == operator your function will return a bool, meaning it can only be trueor false. An equivalent would be something like:

return 5 == 4;

which would return false since 5 is not equal to 4.

Long Answer:

Instead of writing this in a single line you could split it up into more lines of code. Let's just assume that tail, head and N are integer values, then you could write it like this:

int x, y;
x = (tail+1)%N;
y = head%N;
if ( x == y )
{
    return true;
}
else
{
    return false;
}

Now in this code there may be also that %confuses you a bit. The %is called the Modulus Operator and can give you the remainder of arithmetic operations. In a simple example this would mean:

10 % 3 = 1 because 10/3 is 3 with a remainder of 1. So to make it more clear let's just make another example with your specific problem:

Lets just assume that tail=10,head=6 and N=2. Then you would get something like this:

x = (10+1)%2
x = 11 % 2
x = 1

y = 6 % 2
y = 0

y != x

This would return false cause x and y are not equal. ( If you would run your code with the given example values )

To learn more about Modulus you can look here, or just on any other basic C++ Tutorial.

Upvotes: 2

Habib
Habib

Reputation: 223207

this

(tail+1)%N == head%N

returns a boolean value, either true or false. This statement means that after adding 1 to trail (trail + 1) and the remainder obtained after division with N is equal to remainder of head divided with N. % is used for division with remainder

(%). Modulo is the operation that gives the remainder of a division of two values.

Check this link for c++ operators : http://www.cplusplus.com/doc/tutorial/operators/

Upvotes: 3

Some programmer dude
Some programmer dude

Reputation: 409166

It evaluates the expression, and return the result. In this case it's two modulo operations that are compared, and the result is either true or false which will be returned.

Upvotes: 2

enobayram
enobayram

Reputation: 4698

you're returning a boolean value. The value represents whether or not the remainder of (tail+1) divided by N is the same as that of head.

Upvotes: 2

Luchian Grigore
Luchian Grigore

Reputation: 258558

It returns true or false, depending on whether the expression is true or not.

It's the same as:

if ( (tail+1)%N == head%N )
   return true;
else
   return false;

Upvotes: 5

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