Re: floating-point-bits

Oops, bug snuck in at last minute. 64 not 32

(defun make-double-float (bits)
   (declare (type (unsigned-byte 64) bits))  ;<<<<
   (let* ((sgn  (ldb (byte  1 63) bits))
          (exp  (ldb (byte 11 52) bits))
          (mant (ldb (byte 52 0) bits))
          (signif (logior mant (ash 1 52)))
          (sign (if (= sgn 1) -1d0 1d0))
          (expon(- exp 1023 51)))
     (float-sign sign (scale-float (float signif) expon))))


On 2/15/2025 12:24 PM, Paul Werkowski (as pw at snoopy dot qozzy dot 
com) wrote:
> I came across the chapter in the LW UG about TYPED-AREF-VECTOR and 
> friends. It reminded me of a project a long time ago where I wanted to 
> stream real-time floating-point data over a TCP communication link to 
> an analysis client. I came up with code to pack/unpack FP data. Maybe 
> someone would find it useful.
>
> ;;; fp-bits.lisp
>
> ;;;;;;;;;;;;;;;;;;;;;;
> (defun single-float-bits (fpn)
>   (declare (type single-float fpn))
>   ;; 1.5 == 0x3fc00000
>   ;; signif  #x0c00000
>   ;; expon -23
>   (multiple-value-bind (signif expon sign)
>       (integer-decode-float fpn)
>     (let* ((sgn (if (minusp sign) 1 0))
>            (exp (+ 127 expon 23)) ; 23 bits?
>            (man (ldb (byte 23 0) signif)) ; 0x400000
>            (bits exp))
>       (setf bits (dpb sgn (byte 1 31) bits)
>             bits (dpb exp (byte 8 23) bits)
>             bits (dpb man (byte 23 0) bits))
>       bits)))
>
> (defun make-single-float (bits)
>   (declare (type (unsigned-byte 32) bits))
>   (let* ((sgn (ldb (byte 1 31) bits))
>          (exp (ldb (byte 8 23) bits))
>          (mant (ldb (byte 23 0) bits))
>          (signif (logior mant #x800000)) ; (ash 1 23)
>          (sign (if (= sgn 1) -1f0 1f0))
>          (expon(- exp 150)))
>     (float-sign sign (scale-float (float signif) expon))))
>
> (defun double-float-bits (dfn)
>   (declare (type double-float dfn))
>   (multiple-value-bind (signif expon sign)
>       (integer-decode-float #+()decode-float dfn)
>     (let* ((sgn (if (minusp sign) 1 0))
>            (exp (+ 1023 expon 51 )) ; ?
>            (man (ldb (byte 52 0) signif))
>            (bits exp))
>       (setf bits (dpb sgn (byte 1 63) bits)
>             bits (dpb exp (byte 11 52) bits)
>             bits (dpb man (byte 52 0) bits))
>       bits)))
>
> (defun make-double-float (bits)
>   (declare (type (unsigned-byte 64) bits))
>   (let* ((sgn  (ldb (byte  1 63) bits))
>          (exp  (ldb (byte 11 52) bits))
>          (mant (ldb (byte 52 0) bits))
>          (signif (logior mant (ash 1 52)))
>          (sign (if (= sgn 1) -1d0 1d0))
>          (expon(- exp 1023 51)))
>     (float-sign sign (scale-float (float signif) expon))))
>
> ;;;;;;;;;;;;
>
> _______________________________________________
> Lisp Hug - the mailing list for LispWorks users
> [email protected]
> http://www.lispworks.com/support/lisp-hug.html

_______________________________________________
Lisp Hug - the mailing list for LispWorks users
[email protected]
http://www.lispworks.com/support/lisp-hug.html