pow() question

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  • david.corby@gmail.com
    #1

    pow() question

    I would like to know a few things about the pow() function.

    1.) Is it an efficient way to raise a number to a given power for both
    small and large numbers?
    2.) How accurate is pow() when doing integer calculations? I'm
    basically just going to use it to get powers of 10, but I can't have
    pow(10, 6) == 999999 or 1000001 when I bring it back to an integer.
    3.) Is there an integer-only version of pow in the STL that I'm missing
    somewhere? I've found SGI's extension, and __gnu_cxx::powe r, but I'm
    trying to keep my code portable.

    Thanks in advance,
    Dave

    Tags: None
    • John Harrison
      #2
      Re: pow() question


      <david.corby@gm ail.com> wrote in message
      news:1098396719 .387874.255870@ z14g2000cwz.goo glegroups.com.. .[color=blue]
      >I would like to know a few things about the pow() function.
      >
      > 1.) Is it an efficient way to raise a number to a given power for both
      > small and large numbers?
      > 2.) How accurate is pow() when doing integer calculations? I'm
      > basically just going to use it to get powers of 10, but I can't have
      > pow(10, 6) == 999999 or 1000001 when I bring it back to an integer.
      > 3.) Is there an integer-only version of pow in the STL that I'm missing
      > somewhere? I've found SGI's extension, and __gnu_cxx::powe r, but I'm
      > trying to keep my code portable.
      >[/color]

      Really how hard would it be to write your own function? You could even pinch
      the code from __gnu_cxx::powe r, provided you give them credit I'm sure they
      wouldn't mind.

      I think the answer to questions 1 and 2 is implementation dependent. Which
      is why if you have particular requirements you should code it yourself. The
      answer to question 3 is no.

      john


        Comment

        • david.corby@gmail.com
          #3
          Re: pow() question

          Ah, I see. Well, coding my own function isn't a problem, but I was
          looking for the STL to define a function so that I could take advantage
          of it requiring certain results while leaving the implementors free to
          use the best architecture-dependant method they could. Thanks though,
          now I can stop looking and take the 3 minutes it'll take to write :P

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