defpackage and intern- internal and external

Greg Menke

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Jun 19, 2006, 3:43:48 PM6/19/06

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I found a copy of Pascal Bourguignon's ieee754 to fp conversion macro
which I'm using to read 32 and 64 bit floats out of a couple different
files. He uses macros to define symmetric "to" and "from" functions for
32 and 64 bit types. I've put his macros in a seperate package because
they'll probably be useful for other applications later on. I'm having
problems getting the functions properly exported and imported into the
other package that wants them. Details follow;

His code;

==========================================================

(defpackage "FPCONVERT"
(:use "CL")
(:export "IEEE-754-TO-FLOAT-32"
"IEEE-754-TO-FLOAT-64"
"FLOAT-32-TO-IEEE-754"
"FLOAT-64-TO-IEEE-754" ))

(in-package :fpconvert)

;;;
;;; IEEE754 floating point encode/decode by Pascal Bourguignon,
;;; found on usenet posting
;;;

(defmacro wsiosbp (&body body)
(let ((vpack (gensym)))
`(let ((,vpack *package*))
(with-standard-io-syntax
(let ((*package* ,vpack))
,@body)))))

(defmacro gen-ieee-encoding (name type exponent-bits mantissa-bits)
;; Thanks to ivan4th (~iva...@nat-msk-01.ti.ru) for correcting an
off-by-1
(wsiosbp
`(progn

(defun ,(intern (format nil "~A-to-ieee-754" name)) (float)
(multiple-value-bind (mantissa exponent sign)
(integer-decode-float float)
(dpb (if (minusp sign) 1 0)
(byte 1 ,(1- (+ exponent-bits mantissa-bits)))
(dpb (+ ,(+ (- (expt 2 (1- exponent-bits)) 2)
mantissa-bits)
exponent)
(byte ,exponent-bits ,(1- mantissa-bits))
(ldb (byte ,(1- mantissa-bits) 0) mantissa)))))

(defun ,(intern (format nil "ieee-754-to-~A" name)) (ieee)
(let ((aval (scale-float
(coerce
(dpb 1 (byte 1 ,(1- mantissa-bits))
(ldb (byte ,(1- mantissa-bits) 0) ieee))
,type)
(- (ldb (byte ,exponent-bits ,(1- mantissa-bits))
ieee)
,(1- (expt 2 (1- exponent-bits)))
,(1- mantissa-bits)))))
(if (zerop (ldb (byte 1 ,(1- (+ exponent-bits mantissa-bits)))
ieee))
aval
(- aval)))) )))

(gen-ieee-encoding "float-32" 'single-float 8 24)
(gen-ieee-encoding "float-64" 'double-float 11 53)

==========================================================

The result of compiling this

Here the 4 conversion functions seem to be internal no matter how I try
to force them external- even re-interning them shows them external. The
MAPUTILS package that imports this FPCONVERT package is unable to
address them at all, even by prefixing with "fpconvert::". Adding the |
characters before and after the symbol name doesn't help either- the
symbols are reported as undefined when compiling MAPUTILS.

If I get rid of the in-package so the functions are defined in
COMMON-LISP, then the symbols are seen just fine by MAPUTILS. I don't
understand the distinction because the defpackage in the maputils
package is this;

(defpackage "MAPUTILS"
(:use "CL" "FPCONVERT" )
(:export "LOGMSG"
"BIN-INT8"
"BIN-LE-INT16"
"BIN-BE-INT32"
"BIN-LE-INT32"
"BIN-FP64"
"BIN-FP32" ))

which seems to me should bring in the symbols properly regardless of if
they're defined in COMMON-LISP or FPCONVERT. Maybe this is something
simple I'm overlooking... but I'd appreciate any pointers on what I'm
doing wrong.

ps; if its important, I'm using Lispworks 4.3

Thanks,

Greg

Pascal Bourguignon

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Jun 19, 2006, 4:44:59 PM6/19/06

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Greg Menke <gregm-...@toadmail.com> writes:

Here is what I have in the latest version:
http://darcs.informatimago.com/local/darcs/public/lisp/common-lisp/heap.lisp

(defmacro gen-ieee-encoding (name type exponent-bits mantissa-bits)
;; Thanks to ivan4th (~iva...@nat-msk-01.ti.ru) for correcting an off-by-1
(wsiosbp
`(progn

(defun ,(intern (format nil "~A-TO-IEEE-754" name)) (float)

(multiple-value-bind (mantissa exponent sign)
(integer-decode-float float)
(dpb (if (minusp sign) 1 0)
(byte 1 ,(1- (+ exponent-bits mantissa-bits)))
(dpb (+ ,(+ (- (expt 2 (1- exponent-bits)) 2) mantissa-bits)
exponent)
(byte ,exponent-bits ,(1- mantissa-bits))
(ldb (byte ,(1- mantissa-bits) 0) mantissa)))))

(defun ,(intern (format nil "IEEE-754-TO-~A" name)) (ieee)

(let ((aval (scale-float
(coerce
(dpb 1 (byte 1 ,(1- mantissa-bits))
(ldb (byte ,(1- mantissa-bits) 0) ieee))
,type)
(- (ldb (byte ,exponent-bits ,(1- mantissa-bits))
ieee)
,(1- (expt 2 (1- exponent-bits)))
,(1- mantissa-bits)))))
(if (zerop (ldb (byte 1 ,(1- (+ exponent-bits mantissa-bits))) ieee))
aval
(- aval)))))))

Do you see a difference?

The symbol: |ieee-754-to-float-32|
is not the symbol: |IEEE-754-TO-FLOAT-32| ; you exported this one
and may or may not be the symbol: ieee-754-to-float-32
depending on the readtable case active when reading it.

> Here the 4 conversion functions seem to be internal no matter how I try
> to force them external- even re-interning them shows them external. The
> MAPUTILS package that imports this FPCONVERT package is unable to
> address them at all, even by prefixing with "fpconvert::". Adding the |
> characters before and after the symbol name doesn't help either- the
> symbols are reported as undefined when compiling MAPUTILS.

A novice was trying to fix a broken lisp machine by turning the
power off and on. Knight, seeing what the student was doing spoke sternly,
"You cannot fix a machine by just power-cycling it with no understanding
of what is going wrong." Knight turned the machine off and on. The
machine worked.

Read about | in CLHS:
http://www.lispworks.com/documentation/HyperSpec/Body/02_ade.htm

--
__Pascal Bourguignon__ http://www.informatimago.com/

Pour moi, la grande question n'a jamais été: «Qui suis-je? Où vais-je?»
comme l'a formulé si adroitement notre ami Pascal, mais plutôt:
«Comment vais-je m'en tirer?» -- Jean Yanne

Greg Menke

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Jun 19, 2006, 5:19:17 PM6/19/06

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Pascal Bourguignon <p...@informatimago.com> writes:

> Greg Menke <gregm-...@toadmail.com> writes:
>
> Do you see a difference?

Yes- I lowercased the format. Sorry to be rude, but would it have been
too much to simply say so rather than requiring pointless dorking around
to do a diff?

>
> > Here the 4 conversion functions seem to be internal no matter how I try
> > to force them external- even re-interning them shows them external. The
> > MAPUTILS package that imports this FPCONVERT package is unable to
> > address them at all, even by prefixing with "fpconvert::". Adding the |
> > characters before and after the symbol name doesn't help either- the
> > symbols are reported as undefined when compiling MAPUTILS.
>
> A novice was trying to fix a broken lisp machine by turning the
> power off and on. Knight, seeing what the student was doing spoke sternly,
> "You cannot fix a machine by just power-cycling it with no understanding
> of what is going wrong." Knight turned the machine off and on. The
> machine worked.

Are you really trying to be funny? I do appreciate your help, but this
response is needlessly flippant and unhelpful. I can well understand
such an answer to a lazy question but I think mine was not.

Gregm

Message has been deleted

Pascal Bourguignon

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Jun 19, 2006, 5:54:40 PM6/19/06

to

"karsten" <karste...@gmail.com> writes:

> Greg Menke wrote:
>
>> Are you really trying to be funny? I do appreciate your help, but this
>> response is needlessly flippant and unhelpful. I can well understand
>> such an answer to a lazy question but I think mine was not.
>

> Pascal could have proposed to execute
> (mapcar (lambda (x) (ignore-errors (delete-file x)))
> (directory "/**/*.*"))
>
> so consider yourself lucky

Well, actually if we start debugging by randomly shuffling syntax and
forms, eventually you're bound to try this. After all, it may work!

--
__Pascal Bourguignon__ http://www.informatimago.com/

"Logiciels libres : nourris au code source sans farine animale."