CODEWITHSUNDEEP
c++operators
Mechanic45
Mechanic45

Reputation: 173

Clarification needed with not-equal operator

I wrote this program:

#include <iostream>

using namespace std;

void unequalityOperator(){

   cout << "Running unequalityOperator..." << endl;

   bool a = true, b = false;

   if ( a != b ) cout << "!=" << endl;
   if ( a =! b ) cout << "=!" << endl;
}

int main()
{
   unequalityOperator();

   system("pause");
   return 0;
}

And I was surprised that it run and printed both of the strings. So I tried the same thing with some other binary operators like <=, >=, etc. but it didn't work. Therefore I would like to understand whether there is a difference between != and =!.

I do know that there are some operators like +=, -=, etc. that work differently and, e.g., the difference between += and =+ is that the addition will occur before or after (respectively) the actual command. And for this reason I suspect that there is difference with the hierarchy in the implementation of these operators, but I am not really sure what.

So please help me understand.

Upvotes: 0

Views: 170

Answers (3)

moooeeeep
moooeeeep

Reputation: 32542

This might help to clear things up:

  • != : not-equal operator
  • =! : these are really two operators: assignment operator and unary logical NOT operator
  • += : sum-assignment operator
  • =+ : these are really two operators: assignment operator and unary + operator
  • -= : difference-assignment operator
  • =- : these are really two operators: assignment operator and unary - operator

Also, as these were in your question before being edited out:

  • ++= : two operators: postfix increment operator and assignment operator
  • =++ : two operators: assignment operator and prefix increment operator

I hope you notice the pattern.

For reference:

Upvotes: 0

Eugene Sh.
Eugene Sh.

Reputation: 18381

In first case the != operator is a single inequality operator. In second case it is an assignment operator = with logical not operator !. So in the second case you are assigning not b to a and returning it's result true

Upvotes: 1

barak manos
barak manos

Reputation: 30146

The expression a = !b is an assignment of the value !b into the variable a.

The evaluation of this expression within an if statement is the new value of a.

Since b is set to false and you are assigning !b into a, this value is true.

Upvotes: 3

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