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About fallback in C ++

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

I understand the return, but I do not understand it ... What does this mean?

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

Thanks a lot for your patience.

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6 answers


It returns true

or false

, depending on whether the expression is true or not.

This is the same as:



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

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

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



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

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

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you are returning boolean. The value represents whether the remainder (tail + 1) divided by N is the same as that of the head.

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It evaluates the expression and returns the result. In this case, two operations are compared modulo, and the result will be either true

or false

that will be returned.

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

e.g. if tail is 2, head is 1 and N is 2

(tail + 1)% N equals 1

head% N is also 1

so the whole expression returns true

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The short answer is:

Because of the operator, ==

your function will return a value bool

, which means it can only be true

or false

. The equivalent would be something like this:

return 5 == 4;

which will return false

since 5 is not equal to 4.

Long answer:

Instead of writing this on one line, you can split it into multiple lines of code. Suppose that tail

, head

and N

are integer values, then you can write it as follows:

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

Now in this code there may also be, which %

confuses you a little. %

called Modulus Operator

and can give you the rest of the arithmetic operations. In a simple example, this would mean:

10 % 3 = 1

because it 10/3

equals 3 with a remainder of 1. So to make it clearer, let's just do another example with your specific problem:

Suppose that tail=10

, head=6

and N=2

. Then you get something like this:

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

y = 6 % 2
y = 0

y != x

This will return the false

reason x

and are y

not equal. (If you run your code with the given example values)

To learn more about Modulus

, you can take a look here or just on any other basic C ++ tutorial.

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