finding the first bit set to '1'

[Jerry Messina]

I ran across this code and thought it was a neat trick, so I adapted it to SF.
It locates the first bit in a byte that's set to a '1'

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//
// find lowest bit set in a byte
// returns bitmask indicating the first set bit, or 0 if none are set
//
function FindLowestBit(b as byte) as byte
  // this function computes 'result = b and -b'
  // however, the expression 'b and -b' will use 16-bit math by default
  // this assignment will allow the compiler to use bytes instead
  dim bb as byte = -b
  result = b and bb
end function

You can do the same with words...

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function FindLowestBit(w as word) as word
  // use words instead of longwords
  dim ww as word = -w
  result = w and ww
end function

And, if you want to find the first '0' bit instead just pass it the inverse

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y = FindLowestBit(not(x))