int floor(double)?

This is a discussion on int floor(double)? within the C Programming forums, part of the General Programming Boards category; is there a variation of the floor function that accepts a double parameter and returns an int?...

  1. #1
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    int floor(double)?

    is there a variation of the floor function that accepts a double parameter and returns an int?

  2. #2
    Woof, woof! zacs7's Avatar
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    Well, the standard floor() accepts a double and returns a 'whole' double.

    So you could simply cast the result back to an int, ie

    Code:
    int my_floor(double n)
    {
        return (int) floor(n);
    }
    Or something, providing it fits in an integer
    Last edited by zacs7; 03-28-2008 at 09:08 PM.

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    and the Hat of Guessing tabstop's Avatar
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    No. (There are some rounding functions that return long int, like lround.)

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    Woudnt casting it to an int have the same effect as floor()?
    Code:
    int floor(double a)
    {
      return (int)a;
    }
    EDIT: changed "int round(double a)" to "int floor(double a)"
    Last edited by 39ster; 03-28-2008 at 11:10 PM.

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by 39ster View Post
    Woudnt casting it to an int have the same effect as floor()?
    Code:
    int round(double a)
    {
      return (int)a;
    }
    Casting to int truncates, so -9.82 would go to -9, not -10.

  6. #6
    Woof, woof! zacs7's Avatar
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    Cast after you 'floor', truncating the 0 isn't going to mean anything.

    ie, floor 9.82 = 9.0, cast 9.0 = 9

  7. #7
    Aia
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    Quote Originally Posted by 39ster View Post
    Woudnt casting it to an int have the same effect as floor()?
    Code:
    int round(double a)
    {
      return (int)a;
    }
    Code:
    int round(double a)
    {
      return (int) ( a + .5 );
    }
    When the eagles are silent, the parrots begin to jabber. ~Winston Churchill

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    casting worked! lround() doesn't seem to work despite including math.h as a header file.

  9. #9
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by chickenandfries View Post
    casting worked! lround() doesn't seem to work despite including math.h as a header file.
    I thought it was clear from the name, but lround() rounds to nearest and doesn't calculate a floor. Or did you mean that it wasn't there? It's in math.h as of C99 at least.

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    Yes, I used lround() after performing floor(), but the compiler indicated "undefined reference to lround".

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    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by chickenandfries View Post
    is there a variation of the floor function that accepts a double parameter and returns an int?
    The best way to achieve this is exactly as you stated. Pass to floor(), and cast the result to int.

  12. #12
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by chickenandfries View Post
    Yes, I used lround() after performing floor(), but the compiler indicated "undefined reference to lround".
    What compiler? If gcc, be sure to include "-lm" at the end so that the linker finds the math library. If MSVC6, well, that's missing some C99 things. Everything else I'm aware of should have it.

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    Quote Originally Posted by tabstop View Post
    Casting to int truncates, so -9.82 would go to -9, not -10.
    Forgot about negatives :/

    Quote Originally Posted by Aia View Post
    Code:
    int round(double a)
    {
      return (int) ( a + .5 );
    }
    Whoops. I meant int floor(double a), but it woudnt work anyways (as stated by tabstop)
    Last edited by 39ster; 03-28-2008 at 11:10 PM.

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