Hi all
I'm trying to code something to read and write floating point numbers
from/to a binary stream.
Right now I'm stuck into something strange.
I try to compile the following code, and I get an error about a number
beeing to big to be a double-float... I really don't get it :-(
Here's the code :
;;; From Paul Graham's "On Lisp"
(defmacro with-gensyms (syms &body body)
`(let ,(mapcar #'(lambda (s)
`(,s (gensym)))
syms)
,@body))
;;; End of P.G.'s code
(defun read-unsigned-integer (nb-bytes) ;; just to pretend it exists.
(* nb-bytes 8))
(defmacro define-IEEE-float (name
&key (sign-bits 1)
(exponant-bits 8)
(mantissa-bits 23)
(bias 127)
(associated-type 'float))
(with-gensyms (significant exponant sign s-bits e-bits m-bits b
value)
`(defun ,(intern (string-upcase (format nil "read-~s" name))) ()
(let* ((,s-bits ,sign-bits)
(,e-bits ,exponant-bits)
(,m-bits ,mantissa-bits)
(,b ,bias)
(,value (read-unsigned-integer (/ (+ ,s-bits ,e-bits ,m-bits) 8)))
(,significant (+ (ash 1 ,m-bits) (logand (1- (ash 1 ,m-bits))
,value)))
(,exponant (- (logand (1- (ash 1 ,e-bits)) (ash ,value (- ,m-bits)))
,b))
(,sign (ash ,value (- (+ ,e-bits ,m-bits)))))
(* ,significant (expt 2 ,exponant) (expt (coerce -1
,associated-type) ,sign))))))
(define-IEEE-float IEEE-double-float
:sign-bits 1
:exponant-bits 11
:mantissa-bits 52
:bias 1023
:associated-type 'double-float)
It seems there something wrong during the optimization in the
compilation of the function generated by the macro...
Thanks for any hint you could give.
Martin
PS: Sorry about the long lines...
