(in-package :cl-user)

(defun decimal-decode-float (x &optional (lo 61) (hi 63))
  (multiple-value-bind (m k) (integer-decode-float x)
    (let ((j 0) (c 0) s)
      ;; x = m * 2^k * 10^j
      (loop while (< k 0) do
            (incf c)
            (loop while (< m (expt 2 hi)) do (setq m (* m 10)) (decf j))
            (loop while (and (< k 0) (> m (expt 2 lo))) do (setq m (round m 2)) (incf k)))
      (loop while (> k 0) do
            (incf c)
            (loop while (and (> k 0) (< m (expt 2 hi))) do (setq m (* m 2)) (decf k))
            (loop while (> m (expt 2 lo)) do (setq m (round m 10)) (incf j)))
      (setq s (format nil "~DD~D" m j))
      (values m k j
              s
              (= x (read-from-string s))))))