[Home]  [Edit this page]  [Recent Changes]  [Special Pages]  [Help] 

---

CppDecrementOperator

---

(C++) -- operator

The decrement operator is used to lower an int's value by one.

Its opposite operator is the increment operator, ++.

include <cassert>


int i = 1;
--i;
assert(i==0);

Prefer --i to i-- [1].

There are four ways to decrement a value by 1:

1) i = i - 1;  
2) i -= 1;
3) --i;
4) i--;

When you define these 4 ways in a class then ways #1 and #3 produce a temporal copy of it, which might slow down your program unnecessarily. Therefore, #4 will be quicker of equally fast as #3.

Overloading the decrement operator

struct MyInt
{
  //Prefix
  MyInt& operator--()
  {
    --mX;         //Increment
    return *this; //Return class reference
  }
  //Postfix
  MyInt operator--(int)
  {
    MyInt old(*this); //Copy
    --(*this);        //Increment original using prefix
    return old;       //Return old copy
  }
  int mX;
};
int main()
{
  MyInt m;
  --m;
  m--;
}

'Decrement operator' links

• C

Reference

• Bjarne Stroustrup. The C++ Programming Language. 2000. 3rd edition: ISBN: 0-201-88954-4. 2000. Item 19.5.7

[Edit this page]  [Page history]  [What links here]  [Discuss this topic]  [Printer Friendly]