Function: PARSE-IEEE-DOUBLE

Documentation

Given an IEEE 64 bit double representeted as an integer (ie a sequence of 64 bytes), return the coressponding double value

Source

(defun parse-ieee-double (u64)
  "Given an IEEE 64 bit double representeted as an integer (ie a
  sequence of 64 bytes), return the coressponding double value"
  (* (expt -1 (ldb (byte 1 63) u64))
     (expt 2 (- (ldb (byte 11 52) u64) 1023))
     (1+ (float (loop for i from 51 downto 0
                      for n = 2 then (* 2 n)
                      for frac = (* (/ n) (ldb (byte 1 i) u64))
                      sum frac)))))