Thread: Is this the best way to round up a float ?

  1. #1
    Registered User
    Join Date
    Aug 2001

    Is this the best way to round up a float ?


    when casting a float to an int you lose the fractional part of the number . So does the code below round the float up to the next int in the most effective manner. If not could you please show how you would do it?

    #include <iostream>
    using namespace std;

    int main ()


    double num1 = 0;
    int newnum = 0;

    cout << endl << "Please Enter a float number and i Will round it up to the next whole number!"
    << endl;

    cin >> num1;

    newnum = num1 +1;

    cout << newnum
    << endl;

    return 0;

  2. #2
    Skunkmeister Stoned_Coder's Avatar
    Join Date
    Aug 2001
    Why not just use the function that the language provides for this.... ciel() . You will find it in math.h or cmath(where its in namespace std)
    Free the weed!! Class B to class C is not good enough!!
    And the FAQ is here :-

  3. #3
    Registered User
    Join Date
    Aug 2001
    This comes from VB, but ought to work in c++:

    enter a float, add 0.5, then use floor() to round it out. If the float entered was x.5 or above, you'll round up. Below x.5, you'll round down.
    Telling a user to enter a float, but secretly treating it as an int, will only round down. 5.999 will come out as 5, not 6.

  4. #4
    Registered User kitten's Avatar
    Join Date
    Aug 2001
    inline int Round(const double var)
      return var > 0 ? (int)(var + 0.5) : (int)(var - 0.5);
    Making error is human, but for messing things thoroughly it takes a computer

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