pow() doesnt return a double?

This is a discussion on pow() doesnt return a double? within the C++ Programming forums, part of the General Programming Boards category; What does that mean? Can this opcode, whatever it is, be enabled/disabled? Thanx....

  1. #16
    Registered User FloatingPoint's Avatar
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    What does that mean?
    Can this opcode, whatever it is, be enabled/disabled?

    Thanx.
    Come cast your shadow over me
    and I'll cast mine all over thee
    Take me away, into the shades
    where there is no light of day

  2. #17
    Super Moderator VirtualAce's Avatar
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    It means Bubba's answer is only relevant to assembler programmers on x86 machines.

    C and C++ programmers simply look at the prototypes of the functions involved to work out what they return
    Very true, but on all x86 and hybrids thereof (AMD, etc) this is an accurate statement.

    So obviously what is taking place is that somewhere a conversion is being done on the result which is why it is returning as an integral value. I've never had this problem with pow(), but I know why it is happening.

    There is nothing wrong with the pow() function in the math library and if you disassembled the program you could verify this fact. So the problem exists in either how you are using pow() or in how you are displaying the result.

    Unless you are programming on another platform other than x86 or not using C/C++, all floating point values are returned in st(0) or the first floating point register. There is no way possible for pow() to return an integral value since it does not place any integral values into (e)ax which is where all integral values are returned. This statement only applies to C/C++ since this is the system the designers used to be able to return values from functions.

    Salem is right in that you should be able to fix the problem w/o diving into the disassembly.

    <double/float> SomeFunc(void) - implies the result will be left in st(0)

    <unsigned/signed char, int, long> SomeFunc(void) - implies the result will be in (e)ax


    Granted assembler is not used much anymore and is not portable and blah, blah, blah...but it can be useful in debugging and very useful in games. It will give you a better idea of what is taking place in your C code and you will be able to read the disassembly that MSVC puts out.
    Last edited by VirtualAce; 07-31-2003 at 08:56 AM.

  3. #18
    Cat without Hat CornedBee's Avatar
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    No conversion is done. cout formatting simply doesn't output any digits after the comma and thus not the comma either.
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  4. #19
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    It's a decimal point, not a comma you stupid European.

  5. #20
    &TH of undefined behavior Fordy's Avatar
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    Originally posted by golfinguy4
    It's a decimal point, not a comma you stupid European.

    I'm a European and I use a decimal point......kind of throws me whenever I see any figures from the continent....

  6. #21
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    [sarcastic arrogance]Yeah, but you also like our cousin, you learn the best stuff from us.[/sarcastic arrogance]

  7. #22
    Cat without Hat CornedBee's Avatar
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    If you weird guys ever start using any sane units for weight, length etc. we can talk again
    All the buzzt!
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  8. #23
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    When you get a good language (one that doesn't sound like you're coughing up your lungs while you're speaking), we can start talking.

  9. #24
    Cat without Hat CornedBee's Avatar
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    Um, what are you talking about? I'm not Dutch
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