floating point value

This is a discussion on floating point value within the C++ Programming forums, part of the General Programming Boards category; heyas, i was wondering if theres a way to determind if a float has a decimal value? i.e i might ...

  1. #1
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    floating point value

    heyas,

    i was wondering if theres a way to determind if a float has a decimal value?

    i.e i might have the following times

    24:00
    09:00
    14:30

    i want to know if i can iterate through an array or any collection and test if the '.30' exists.

    or even more simply a function like isDecimal()

    tia

    -twans

  2. #2
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    my appologies,

    those times should read:

    24.00
    09.00
    14.30

    as im storing them as floats! :P

  3. #3
    Senior Member joshdick's Avatar
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    If the number minus the floor of the number is anything other than zero, then there are values stored after the decimal place.

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    The only thing I can think of, is to subtract .30 from the number, and then use the modulus operator with a 1. If it was n.30, your answer will be 1.

    Remember though, that floating point values can never be trusted to be exact, so don't use the == operator to test if it's 1. You could find the absolute value of (1 - yourNumber), and then test to see if that number is less then .1 or something.

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    works a charm,

    those that are interested
    Code:
    #include <cmath>
    
    floor(float);
    thanks for your help josh

    -twan

    [edit: silly typo on the include]
    Last edited by twans; 04-07-2005 at 08:40 AM.

  6. #6
    Senior Member joshdick's Avatar
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    You're welcome.

    The standard library function floor() is in <cmath>. What is <floor>?

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    can the modulus operator be used on floats?

    -thanks for the reply too sean.
    Last edited by twans; 04-07-2005 at 08:44 AM.

  8. #8
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    Modulus only works on ints I believe.

    You could get dirty and cast to int and back to float... something like this:

    Code:
    float x = 3.2f;
    bool hasDecimal = x != (float)((int)x);
    Note: this code hasn't been tested, I just wanted to get the idea across
    Last edited by TheColonial; 04-07-2005 at 08:53 AM. Reason: Changed == to !=

  9. #9
    Senior Member joshdick's Avatar
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    There's an fmod(float x, float y) function in <cmath> that returns the remainder of x/y.

  10. #10
    Registered User hk_mp5kpdw's Avatar
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    Quote Originally Posted by twans
    can the modulus operator be used on floats?

    -thanks for the reply too sean.
    Use the fmod function to calculate modulus on floating-point values.

    [edit]Darn... beaten! [/edit]
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

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