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Groups > comp.lang.forth > #21646
| From | anton@mips.complang.tuwien.ac.at (Anton Ertl) |
|---|---|
| Newsgroups | comp.lang.forth |
| Subject | Re: Portability |
| Date | 2013-04-13 11:59 +0000 |
| Organization | Institut fuer Computersprachen, Technische Universitaet Wien |
| Message-ID | <2013Apr13.135920@mips.complang.tuwien.ac.at> (permalink) |
| References | (1 earlier) <gLGdnaPZpbm3TPrMnZ2dnUVZ_qydnZ2d@supernews.com> <2013Apr12.154339@mips.complang.tuwien.ac.at> <D4SdnUAv5-fwrPXMnZ2dnUVZ_vydnZ2d@supernews.com> <5168577e$0$26887$e4fe514c@dreader37.news.xs4all.nl> <qaCdnRznMZtugPTMnZ2dnUVZ_s6dnZ2d@supernews.com> |
Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>Albert van der Horst <albert@spenarnc.xs4all.nl> wrote:
>> In article <D4SdnUAv5-fwrPXMnZ2dnUVZ_vydnZ2d@supernews.com>,
>> Andrew Haley <andrew29@littlepinkcloud.invalid> wrote:
>>>Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
>>>> Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>>>>>Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
>>>>>> Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>>>>>>>Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
>>>>>>>> Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>>>>>>>>>Albert van der Horst <albert@spenarnc.xs4all.nl> wrote:
>>>>>>>>>> It clearly states that < is supposed
>>>>>>>>>> to work on signed numbers. So the behaviour you describe would be a
>>>>>>>>>> defect ("or bug") as in "deviation from the specification".
>>>>>>>>>
>>>>>>>>>Not really, no, any more than this is a deviation from the
>>>>>>>>>specification:
>>>>>>>>>
>>>>>>>>>2147483647 dup + . -2 ok
...
>>>fig-FORTH's actual < is
>>>
>>>: < - 0< ;
>>>
>>>I'm looking at the original source code.
>>
>> Okay. It is a curious historical side note.
>> I've looked into 6 or 7 versions (mostly even in print) and they
>> differ from this.
>
>Sure, but it's the fig-FORTH model (for 6502, written in Forth) on
>which all the others were based
So the first implementation contained a bug, or they would not have
changed it. So they did not share your idea that it is "not really,
no" a bug.
Although, looking at two versions, the code looks still funny:
6502 v1.1:
L1254 .BYTE $81,$BC
.WORD L1246 ; link to U<
LESS .WORD *+2
SEC
LDA 2,X
SBC 0,X ; subtract
LDA 3,X
SBC 1,X
STY 3,X ; zero high byte
BVC L1258
EOR #$80 ; correct overflow
L1258 BPL L1260
INY ; invert boolean
L1260 STY 2,X ; leave boolean
JMP POP
8086 v1.0:
DB 81H
DB '<'+80H
DW EQUAL-4
LESS DW $+2
POP DX
POP AX
MOV BX,DX
XOR BX,AX ; T E S T FOR EQUAL S I G N S
JS LES1 ; SIGNS NOT T H E SAME
SUB AX,DX
LES 1: OR AX, AX ; TEST SIGN S I T
MOV AX ,0 ; ASSUME FALSE C O N D I T I O N
JNS LES2 ; NOT L E S S TEEN
INC AX ; TRUE (1)
LES2: JMP APUSH
It seems the authors did not like the cmp instructions of these
architectures. I am not sure that these implementations are correct.
Correct implementations that are shorter are certainly possible.
What's even funnier is:
6502 v1.1:
; U<
; Unsigned less than
;
L1246 .BYTE $82,'U',$BC
.WORD L1244 ; link to =
ULESS .WORD DOCOL
.WORD SUB ; subtract two values
.WORD ZLESS ; test sign
.WORD SEMIS
Why have U< if you are implementing circular comparison? And vice
versa, why implement U< as circular comparison?
Concerning your integer overflow argument, I found this within two
minutes of reading the "Installation Manual and Glossary"
<http://www.forth.org/fig-forth/contents.html>:
|Unless otherwise noted, all references to numbers are for 16 bit signed
|integers. [...]
|
|All arithmetic is implicitly 16 bit signed integer math, with error and
|under-flow indication unspecified.
So wraparound on overflow is compliant with the specification,
circular comparison for < is not.
- anton
--
M. Anton Ertl http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
New standard: http://www.forth200x.org/forth200x.html
EuroForth 2013: http://www.euroforth.org/ef13/
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Portability kenney@cix.compulink.co.uk - 2013-04-06 04:12 -0500
Re: Portability albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-06 11:31 +0000
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-06 10:34 -1000
Re: Portability "Ed" <invalid@nospam.com> - 2013-04-09 09:56 +1000
Re: Portability albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-09 01:30 +0000
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-09 07:21 +0000
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-08 22:18 -1000
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-09 12:41 +0000
Re: Portability Coos Haak <chforth@hccnet.nl> - 2013-04-09 17:21 +0200
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-09 08:06 -1000
Re: Portability Bernd Paysan <bernd.paysan@gmx.de> - 2013-04-09 22:34 +0200
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-09 12:05 -1000
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-09 14:19 -1000
Re: Portability Chris <xrissmith@me.com> - 2013-04-09 20:45 -0700
Re: Portability "Ed" <invalid@nospam.com> - 2013-04-10 14:02 +1000
Re: Portability Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-04-09 23:00 -0700
Re: Portability "WJ" <w_a_x_man@yahoo.com> - 2013-04-12 14:41 +0000
Re: Portability "Ed" <invalid@nospam.com> - 2013-04-13 15:34 +1000
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-10 15:19 +0000
Re: Portability albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-10 11:46 +0000
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-10 15:03 +0000
Re: Portability Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-04-09 18:28 -0700
Re: Portability Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-04-09 17:00 -0700
Re: Portability "Ed" <invalid@nospam.com> - 2013-04-10 13:00 +1000
Re: Portability albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-10 11:55 +0000
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-10 10:10 -0500
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-10 15:56 +0000
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-10 16:18 -0500
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-11 13:24 +0000
Re: Portability Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-04-11 20:50 -0700
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-12 04:17 -0500
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-12 13:43 +0000
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-12 11:08 -0500
Re: Portability albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-12 18:50 +0000
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-13 03:57 -0500
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-13 11:59 +0000
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-13 14:47 -0500
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-12 10:44 -0400
Re: Portability Bernd Paysan <bernd.paysan@gmx.de> - 2013-04-15 16:20 +0200
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-16 08:12 -1000
Re: Portability "A.K." <akk@nospam.org> - 2013-04-16 22:21 +0200
Re: Portability Bernd Paysan <bernd.paysan@gmx.de> - 2013-04-16 22:33 +0200
Re: Portability "Ed" <invalid@nospam.com> - 2013-04-19 15:04 +1000
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-15 15:46 +0000
Re: Portability Sieur de Bienville <morrimichael@gmail.com> - 2013-04-15 19:19 -0700
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-16 12:53 +0000
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-16 17:29 -0400
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-16 11:44 -1000
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-16 18:00 -0400
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-16 17:33 -0500
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-16 12:46 -1000
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-17 13:09 -0400
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-17 12:20 -0500
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-17 07:38 -1000
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-17 16:43 -0500
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-17 20:03 -0400
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-18 16:53 -0500
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-18 18:02 -0400
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-19 03:30 -0500
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-19 15:31 -0400
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-22 09:59 +0000
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-22 07:28 -0500
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-22 15:27 +0000
Re: Portability Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-04-22 18:16 -0700
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-17 10:23 +0000
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-17 13:46 -0400
Re: Portability anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-22 09:47 +0000
Re: Portability Brad Eckert <hwfwguy@gmail.com> - 2013-04-17 10:32 -0700
Re: Portability nobody@nowhere - 2013-04-17 17:36 +0000
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-17 14:21 -0400
Re: Portability Brad Eckert <hwfwguy@gmail.com> - 2013-04-17 15:03 -0700
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-17 18:22 -0400
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-17 18:24 -0400
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-18 00:51 -0400
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-18 17:19 -0400
Re: Portability Brad Eckert <hwfwguy@gmail.com> - 2013-04-19 12:37 -0700
Re: Portability rickman <gnuarm@gmail.com> - 2013-04-19 15:53 -0400
Re: Portability Lars Brinkhoff <lars.spam@nocrew.org> - 2013-04-17 19:26 +0200
Re: Portability albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-10 18:50 +0000
Re: Portability Bernd Paysan <bernd.paysan@gmx.de> - 2013-04-10 22:14 +0200
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-12 04:18 -0500
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-12 08:30 -1000
Re: Portability albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-12 18:58 +0000
Re: Portability "Elizabeth D. Rather" <erather@forth.com> - 2013-04-12 11:29 -1000
Re: Portability "Ed" <invalid@nospam.com> - 2013-04-13 14:57 +1000
Re: Portability Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-09 04:11 -0500
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