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aw/twos-complement.md

Created October 12, 2020 09:42
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Twos complement and reverse in PicoLisp
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twos-complement.md

This obtains the twos complement of a signed integer (from signed -> unsigned), or reverse (from unsigned -> signed)

  • Int: an positive or negative integer
  • Size: expressed in bits (ex: 8, 16, 32, 64...)
(de twos-complement (Int Size)
  (if (lt0 Int)
      (+ Int (>> (- Size) 1))
      (if (=0 (& Int (>> (- (- Size 1)) 1)))
          Int
          (- Int (>> (- Size) 1)) ]
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