OpenEuphoria

Bit-shifting

• Posted by Pete Eberlein <xseal at HARBORSIDE.COM> May 03, 1997
• 846 views

Will bit-shifting operators be available in the next version of
Euphoria?  I would much rather use a built-in machine code instead of a
multiply or divide.  Does Euphoria optimize multiplication into a shift
when one of the numbers is an integer power of two?  Does it convert a
value to floating-point when dividing?

I would much rather be able to
        integer SHR 1   -- shift right
        integer SAR 1   -- shift arithmetic right  (keeps the sign)
instead of using
        floor(integer / 2)

If bit-shifting becomes available I would like a function that does bit
slicing.  It would work with integers the same way as sequences, without
having to convert the integer into a sequence of integers and back
again.  I think it could be coded like this:
  -- returns source[lower_bit..upper_bit]
  function bit_slice(source, lower_bit, upper_bit)
    integer mask
    mask = #FFFFFFFF shr (32 - upper_bit + lower_bit)
    source = source shr lower_bit
    return and_bits(source, mask)
  end function

  -- returns dest with [lower_bit..upper_bit] overwritten by source
  function bit_splice(source, dest, lower_bit, upper_bit)
    integer mask
    mask = (#FFFFFFFF shr (32 - upper_bit + lower_bit)) shl lower_bit
    source = source shl lower_bit
    return or_bits(and_bits(dest, not_bits(mask)), and_bits(source,
mask))
  end function

I could see a lot of code optimizations using these functions.  Speed is
one thing I like about Euphoria, and I would like to see it pushed to
the absolute max.

Also would it be possible to have a 32-bit peek and poke for integers?

Thanks

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