hex2signed function written in Gauche

gistfile1.txt

(define bit-reversal
  (lambda (str)
    (let inner ((len (string-length str)) (instr str) (outstr ""))
	 (if (eq? 0 len)
	     outstr
	   (inner (- len 1)
		  (substring instr 1 (string-length instr))
		  (string-append outstr
				 (cond ((string=? (substring instr 0 1) "0") "1")
				       ((string=? (substring instr 0 1) "1") "0"))))))))


(define bit2signed
  (lambda (str)
    (cond ((string=? "1" (substring str 0 1))
	   (* -1.0 (+ 1 (string->number (string-append "#b" (bit-reversal (substring str 1 (string-length str))))))))
	  (else
	   (* 1.0 (string->number (string-append "#b" (substring str 1 (string-length str)))))))))