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Compare a double to an integer

This is a discussion on Compare a double to an integer within the C Programming forums, part of the General Programming Boards category; Given this code Code: double x=1.00,y=2,z=4; if (y/z||++x) x+=y/z; printf("%f\n",x); So (y/z||++x) is true if at least one expression is ...

  1. #1
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    Compare a double to an integer

    Given this code
    Code:
    double x=1.00,y=2,z=4;
    if (y/z||++x)
          x+=y/z;
    printf("%f\n",x);
    So (y/z||++x) is true if at least one expression is true, that is either (y/z)!=0 or (++x)!=0 or both. I wonder how the comparison is done? Is (y/z) be truncated to integer or 0 be promoted to double?

  2. #2
    Cat
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    In general, when mixing integers and doubles in an expression, the integers are promoted to doubles, but they are promoted only when necessary to evaluate a specific operation (all operations occur only on equal types).

    What I mean is, 1 / 3 + 0.1 will return a double, but it will do 1/3 as integer math first (since it's sooner in the order of operations), yielding 0, and then the addition happens. 0 is promoted to 0.0 and added to 0.1 to yield a final answer of 0.1
    Last edited by Cat; 02-24-2013 at 09:16 AM.
    You ever try a pink golf ball, Wally? Why, the wind shear on a pink ball alone can take the head clean off a 90 pound midget at 300 yards.

  3. #3
    Cat
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    FYI the type promotion list is as follows:

    Long double
    Double
    Float
    Unsigned long int
    Long int
    Unsigned int
    Int

    When an operator has two differently typed operands, the lower operand on the list is promoted to be the same as the higher, even if there is the possibility to introduce errors (e.g. unsigned int - signed int does an unsigned operation.

    Any argument shorter than an int is automatically promoted to an int anyway when used in a mathematical expression, even if this is unnecessary for the argument type (e.g. short + short math is actually int + int math).
    drawar likes this.
    You ever try a pink golf ball, Wally? Why, the wind shear on a pink ball alone can take the head clean off a 90 pound midget at 300 yards.

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