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D - Bug: Package names cannot start with digit.

reply "Robert Medeiros" <robert.medeiros utoronto.ca> writes:
Writing a module declaration like, e.g. 'module graphics.3d.mesh;' crashes
dmd 0.51 after displaying this error message:

position.d(5): ';' expected
position.d(5): no identifier for declarator

with this crash info (FWIW):

DMD caused an invalid page fault in
module DMD.EXE at 0177:004040c5.
Registers:
EAX=0070b038 CS=0177 EIP=004040c5 EFLGS=00010216
EBX=ccccd000 SS=017f ESP=006efd04 EBP=00000472
ECX=00850604 DS=017f ESI=0070b044 FS=3f8f
EDX=00000000 ES=017f EDI=0070b038 GS=3f7e
Bytes at CS:EIP:
8b 13 56 89 d9 ff 52 14 50 e8 fd d4 07 00 83 c4
Stack dump:
0070aa8c 00850604 00850604 00423388 0070b038 00704ef4 0070b038 00000000
00000000 00704f1c bff713e2 00000177 bff712c5 00003e83 c1758400 bff765d5

Rob
Jan 28 2003
parent reply Ilya Minkov <midiclub 8ung.at> writes:
Though crashing is undesired behaviour, "3d" is not a valid identifier.

I quote from D manual, "Lexical":

"Identifiers start with a letter or _, and are followed by any number of 
letters, _ or digits. Identifiers can be arbitrarilly long, and are case 
sensitive. Identifiers starting with __ are reserved."

Which is consistent with C behaviour.  Not only C. You wouldn't name a 
variable "3d", would you? :> And lexing engine is simply the same.

Not a reason enough for a pagefault, nontheless.

-i.

Robert Medeiros wrote:

 Writing a module declaration like, e.g. 'module graphics.3d.mesh;' crashes
 dmd 0.51 after displaying this error message:
 
 position.d(5): ';' expected
 position.d(5): no identifier for declarator
 
 with this crash info (FWIW):
 
 DMD caused an invalid page fault in
 module DMD.EXE at 0177:004040c5.
 Registers:
 EAX=0070b038 CS=0177 EIP=004040c5 EFLGS=00010216
 EBX=ccccd000 SS=017f ESP=006efd04 EBP=00000472
 ECX=00850604 DS=017f ESI=0070b044 FS=3f8f
 EDX=00000000 ES=017f EDI=0070b038 GS=3f7e
 Bytes at CS:EIP:
 8b 13 56 89 d9 ff 52 14 50 e8 fd d4 07 00 83 c4
 Stack dump:
 0070aa8c 00850604 00850604 00423388 0070b038 00704ef4 0070b038 00000000
 00000000 00704f1c bff713e2 00000177 bff712c5 00003e83 c1758400 bff765d5
 
 Rob
Jan 28 2003
parent reply "Robert Medeiros" <robert.medeiros utoronto.ca> writes:
 Though crashing is undesired behaviour, "3d" is not a valid identifier.


Thanks - I wasn't sure at first if this was a bug or a feature (excluding
the crash).


 I quote from D manual, "Lexical":


[snip]

 Which is consistent with C behaviour.  Not only C. You wouldn't name a
 variable "3d", would you? :> And lexing engine is simply the same.


Somehow package "threed" just doesn't have the same ring... :)

Rob
Jan 28 2003
parent reply "Sean L. Palmer" <seanpalmer directvinternet.com> writes:
In the math lexicon, it's called R3.  You could use that.  Except they
usually use that funny olde-english style R.  ;)

There's nothing particularly special about 3 dimensions anyway.  And 3D or
2D math and transformations certainly aren't limited in use to just
graphics.  So I question the structure of your library.  Do you have a 2D
mesh, or a 4D mesh?

Sean

"Robert Medeiros" <robert.medeiros utoronto.ca> wrote in message
news:b17cr4$2qg1$1 digitaldaemon.com...

 Which is consistent with C behaviour.  Not only C. You wouldn't name a
 variable "3d", would you? :> And lexing engine is simply the same.


 Somehow package "threed" just doesn't have the same ring... :)

 Rob
Jan 28 2003
parent reply "Robert Medeiros" <robert.medeiros utoronto.ca> writes:
Hi Sean,


 There's nothing particularly special about 3 dimensions anyway.  And 3D or
 2D math and transformations certainly aren't limited in use to just
 graphics.  So I question the structure of your library.  Do you have a 2D
 mesh, or a 4D mesh?


Actually, I invented that module name for illustration, but it was prompted
by an example from the library I'm working on. That's an implementation of
the conformal model of geometric algebra, for a research project related to
computer vision. Some of the code is generic, i.e. applicable to blades and
multivectors of arbitrary dimension (for which I'm trying to apply D
templates), but more often that not for my purposes I can get away with
hand-crafted code for algebraic entities of fixed dimension (1 -> 5) which
can be tweaked for efficiency, hence the 1d, 2d, etc. Your suggestion for
using 'rN' notation is a good one that I think I'll adopt. Thanks!

As for the gothic 'R' notation: maybe if we get to the point where we can
use UTF-?? for our source files... :)

Rob
Jan 29 2003
next sibling parent reply "Walter" <walter digitalmars.com> writes:
"Robert Medeiros" <robert.medeiros utoronto.ca> wrote in message
news:b184a6$srp$1 digitaldaemon.com...

 As for the gothic 'R' notation: maybe if we get to the point where we can
 use UTF-?? for our source files... :)


You can as of 0.51. But identifiers are still ascii.
Jan 29 2003
next sibling parent reply "Robert Medeiros" <robert.medeiros utoronto.ca> writes:
 As for the gothic 'R' notation: maybe if we get to the point where we




can

 use UTF-?? for our source files... :)


 You can as of 0.51. But identifiers are still ascii.


Probably for the best. Otherwise, it would be entertaining for an hour or so
to write all my identifiers in, say, Chinese ideographs -- after which it
would just be confusing and a maintenance nightmare. But think of the
obfuscated coding contests that one could win with a "feature" like that...
one could write a veritable program of Babel... :)

Rob
Jan 29 2003
parent reply factory <tehdasX optushome.com.au> writes:
In article <b19hn4$21fk$1 digitaldaemon.com>, 
robert.medeiros utoronto.ca says...

 As for the gothic 'R' notation: maybe if we get to the point where we




 can

 use UTF-?? for our source files... :)


 You can as of 0.51. But identifiers are still ascii.


 
 Probably for the best. Otherwise, it would be entertaining for an hour or so
 to write all my identifiers in, say, Chinese ideographs -- after which it
 would just be confusing and a maintenance nightmare. 


  Well if the maintainer doesn't read chinese, it prolly would be. But 
for those who can read chinese that prolly wouldn't be a problem. 
  Hmm makes me wonder how most non-english fluent ppl deal with 
identifiers. After some looking about in usenet, it seems that non- 
english language users either just deal with the restrictions of ascii, 
or write their own hacks to make it so that identifiers can be used in 
their language (either by preprocessing, or changing the parser).
  This would seem to a bad way of doing it.


 But think of the
 obfuscated coding contests that one could win with a "feature" like that...
 one could write a veritable program of Babel... :)


  If I was entering I'd try and do it all with symbols.. :)

  - Factory
Feb 01 2003
parent reply "Daniel Yokomiso" <daniel_yokomiso yahoo.com.br> writes:
"factory" <tehdasX optushome.com.au> escreveu na mensagem
news:MPG.18a73d5f6a792070989684 news.digitalmars.com...

[snip]


   Well if the maintainer doesn't read chinese, it prolly would be. But
 for those who can read chinese that prolly wouldn't be a problem.
   Hmm makes me wonder how most non-english fluent ppl deal with
 identifiers. After some looking about in usenet, it seems that non-
 english language users either just deal with the restrictions of ascii,
 or write their own hacks to make it so that identifiers can be used in
 their language (either by preprocessing, or changing the parser).
   This would seem to a bad way of doing it.


 But think of the
 obfuscated coding contests that one could win with a "feature" like




that...

 one could write a veritable program of Babel... :)


   If I was entering I'd try and do it all with symbols.. :)

   - Factory


I'm brazilian and lot's of programmers around here aren't fluent in english.
Usually people use plain ascii without any kind of special characters (even
in Java), but with portuguese identifiers. Most of our accents (e.g. ~ ` ´)
and the "ç" letter are just avoided. So instead of "exceção" (I don't know
if it'll be displayed correctly) is written "excecao" and people don't
complain ;-)


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Feb 02 2003
next sibling parent reply Ilya Minkov <midiclub tiscali.de> writes:
Daniel Yokomiso wrote:

 "factory" <tehdasX optushome.com.au> escreveu na mensagem
 news:MPG.18a73d5f6a792070989684 news.digitalmars.com...
 
 [snip]
 
 

  Well if the maintainer doesn't read chinese, it prolly would be. But
for those who can read chinese that prolly wouldn't be a problem.
  Hmm makes me wonder how most non-english fluent ppl deal with
identifiers. After some looking about in usenet, it seems that non-
english language users either just deal with the restrictions of ascii,
or write their own hacks to make it so that identifiers can be used in
their language (either by preprocessing, or changing the parser).
  This would seem to a bad way of doing it.




People which can't get even a couple of words in English right are a 
major plague in any SW development:
  - english thesis/documents have to be read and worked into software to 
make it modern and efficient: Even the japanese who are "systematically 
taught in school to hate english" prefer english for scientific work.
  - many people aren't able to switch between languages. I'm fluent with 
english, german, and russian, and understand another couple more, but i 
always get headaches when i see laguages mixed together. Language 
keywords are english, identifiers are german (some of them). Horrible, 
it slows me down reading the code by a factor of at least 2. Someone was 
irritated here at first, when i in my home assignment have renamed each 
and every identifier into english, and also wrote all of my comments in 
english as well. I work a lot with finnish guys, imagine what a 
catastrophe it would be if they would write comments in finnish, or i in 
german/russian/whatever... I thow away any piece of source, which 
contains russian, even though i could read it. My editor can't. :>

BTW, i hope you excuse me that i use capitals in text very sparigly, but 
i'm really fed up with them, since in german every noun is capitalised. 
My capitalization threshold is being eaten up by both that and programming.


But think of the
obfuscated coding contests that one could win with a "feature" like
that...






D is not for obfuscation. What i have always liked about Delphi, is that 
foreign code is almost like mine, so i had no major reading problems. D 
was intended to have the same advantage.


 I'm brazilian and lot's of programmers around here aren't fluent in english.
 Usually people use plain ascii without any kind of special characters (even
 in Java), but with portuguese identifiers. Most of our accents (e.g. ~ ` ´)
 and the "ç" letter are just avoided. So instead of "exceção" (I don't know
 if it'll be displayed correctly) is written "excecao" and people don't
 complain ;-)


Most russian programmers are also used to write with ASCII. They call it 
"Volapyuk encoding". Russian has a completely different set of letters, 
which is also by about 10 larger than latin, and lies completely in "bit 
7 set" area.

-i.
Feb 03 2003
parent Evan McClanahan <evan dontSPAMaltarinteractive.com> writes:
Ilya Minkov wrote:

 I'm brazilian and lot's of programmers around here aren't fluent in 
 english.
 Usually people use plain ascii without any kind of special characters 
 (even
 in Java), but with portuguese identifiers. Most of our accents (e.g. ~ 
 ` ´)
 and the "ç" letter are just avoided. So instead of "exceção" (I don't 
 know
 if it'll be displayed correctly) is written "excecao" and people don't
 complain ;-)


 
 
 Most russian programmers are also used to write with ASCII. They call it 
 "Volapyuk encoding". Russian has a completely different set of letters, 
 which is also by about 10 larger than latin, and lies completely in "bit 
 7 set" area.


I've been working in the Czech Republic, and they do the same thing that 
Daniel was talking about.  just write the word without any of the 
diacritical marks.  It can get really confusing if you're not a native 
speaker, since the diacriticals disambiguate the words a lot.  You get a 
feeling for it after a while, but wow, can it be a pain in the ass to 
parse.

Evan
Feb 03 2003
prev sibling parent reply "Sean L. Palmer" <seanpalmer directvinternet.com> writes:
"Daniel Yokomiso" <daniel_yokomiso yahoo.com.br> wrote in message
news:b1kf9f$1k2l$1 digitaldaemon.com...

 I'm brazilian and lot's of programmers around here aren't fluent in


english.

 Usually people use plain ascii without any kind of special characters


(even

 in Java), but with portuguese identifiers. Most of our accents (e.g. ~ `


´)

 and the "ç" letter are just avoided. So instead of "exceção" (I don't know
 if it'll be displayed correctly) is written "excecao" and people don't
 complain ;-)


Well, wouldn't it be nice if you could just program with Portuguese
identifiers?  Sure, you'd have to learn the English D keywords (or use a
preprocessor to translate those too)

I would estimate that at least 50% of all the programs that are made are
never seen by anyone but their maker.  Little test apps and such.

If you don't like accented characters, you could always have a policy
against using them.  I think it's a nice option though for
non-native-English-speakers, and as a nice aside it gets the Unicode ball
rolling.  ;)

Sean
Feb 03 2003
next sibling parent Russell Lewis <spamhole-2001-07-16 deming-os.org> writes:
Sean L. Palmer wrote:

 "Daniel Yokomiso" <daniel_yokomiso yahoo.com.br> wrote in message
 news:b1kf9f$1k2l$1 digitaldaemon.com...
 

I'm brazilian and lot's of programmers around here aren't fluent in


 
 english.
 

Usually people use plain ascii without any kind of special characters


 
 (even
 

in Java), but with portuguese identifiers. Most of our accents (e.g. ~ `


 
 ´)
 

and the "ç" letter are just avoided. So instead of "exceção" (I don't know
if it'll be displayed correctly) is written "excecao" and people don't
complain ;-)


 
 
 Well, wouldn't it be nice if you could just program with Portuguese
 identifiers?  Sure, you'd have to learn the English D keywords (or use a
 preprocessor to translate those too)
 
 I would estimate that at least 50% of all the programs that are made are
 never seen by anyone but their maker.  Little test apps and such.
 
 If you don't like accented characters, you could always have a policy
 against using them.  I think it's a nice option though for
 non-native-English-speakers, and as a nice aside it gets the Unicode ball
 rolling.  ;)
 
 Sean


Unicode itentifiers and translated keywords sound like another thing 
IDEs could do easily.

I'm getting more and more enthralled with the idea of IDEs that do more 
than just colorize your code, or finish an identifier name...IDEs that 
really change the presentation of the code at a more fundamental level.

Frankly, a lot of the features we've suggested at various times 
(operator overloading, inline function call syntax, even templates) 
could be done by the IDE acting as a preprocessor.
Feb 04 2003
prev sibling parent reply Daniel Yokomiso <Daniel_member pathlink.com> writes:
In article <b1nsls$1186$1 digitaldaemon.com>, Sean L. Palmer says...

"Daniel Yokomiso" <daniel_yokomiso yahoo.com.br> wrote in message
news:b1kf9f$1k2l$1 digitaldaemon.com...

 I'm brazilian and lot's of programmers around here aren't fluent in


english.

 Usually people use plain ascii without any kind of special characters


(even

 in Java), but with portuguese identifiers. Most of our accents (e.g. ~ `


´)

 and the "ç" letter are just avoided. So instead of "exceção" (I don't know
 if it'll be displayed correctly) is written "excecao" and people don't
 complain ;-)


Well, wouldn't it be nice if you could just program with Portuguese
identifiers?  Sure, you'd have to learn the English D keywords (or use a
preprocessor to translate those too)

I would estimate that at least 50% of all the programs that are made are
never seen by anyone but their maker.  Little test apps and such.

If you don't like accented characters, you could always have a policy
against using them.  I think it's a nice option though for
non-native-English-speakers, and as a nice aside it gets the Unicode ball
rolling.  ;)

Sean


Actually I wouldn't like it. Most of the libraries I use are written in english
(maybe all of them, but now I don't want to review it ;-) ). It's very weird to
write: "File algumArquivo = new File('temp.txt');" instead of "File someFile =
new File('temp.txt');". It's not only the keywords, but every library you use.
If you stick to english the context changes will be less frequent. But YMMV.
Feb 04 2003
parent "Carlos Santander B." <carlos8294 msn.com> writes:
"Daniel Yokomiso" <Daniel_member pathlink.com> escribió en el mensaje
news:b1pohj$2789$1 digitaldaemon.com...
| Actually I wouldn't like it. Most of the libraries I use are written in
english
| (maybe all of them, but now I don't want to review it ;-) ). It's very
weird to
| write: "File algumArquivo = new File('temp.txt');" instead of "File
someFile =
| new File('temp.txt');". It's not only the keywords, but every library you
use.
| If you stick to english the context changes will be less frequent. But
YMMV.
|
|

I don't find it weird at all. As long as I can, I write all my code in
Spanish. What you said is very relative...

—————————————————————————
Carlos Santander


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Feb 04 2003
prev sibling parent reply "Sean L. Palmer" <seanpalmer directvinternet.com> writes:
What are the plans for extending identifiers to support Unicode?  How far
are you willing to go?  ;)

At very least, accented latin characters should be accepted in identifiers.
It might be nice if the language ignored the accents (but then again I think
case should be ignored too).

I *really* want to be able to use the extra math symbols in Unicode as
operators.  I could give you either a short list or a long list of the ones
I would want.  Just allowing any Unicode character that is considered a
symbol or mathematical operator would be fine too.

The ones that are most direly needed are

dot product (U+22C5 although there are several similar symbols)
cross product  (U+00D7)

The reason we need these is that they're ultra common operations that have
higher precedence than multiply, meaning none of the available overloadable
operators has the right precedence.

but it'd also be nice to have:

division operator (U+00F7)
set union and intersection
set membership
logical operators (and, or, xor, nor, nand, not)
comparison operators (single symbol support for <=, >=, !=, etc plus "almost
equal" for floats)
single symbol support for <<, >>

And I could go on and on.

Sean

----- Original Message -----
From: "Walter" <walter digitalmars.com>
Newsgroups: D
Sent: Wednesday, January 29, 2003 10:40 AM
Subject: Re: Bug: Package names cannot start with digit.



 "Robert Medeiros" <robert.medeiros utoronto.ca> wrote in message
 news:b184a6$srp$1 digitaldaemon.com...

 As for the gothic 'R' notation: maybe if we get to the point where we




can

 use UTF-?? for our source files... :)


 You can as of 0.51. But identifiers are still ascii.
Jan 30 2003
parent "Walter" <walter digitalmars.com> writes:
"Sean L. Palmer" <seanpalmer directvinternet.com> wrote in message
news:b1bst9$15nl$1 digitaldaemon.com...

 What are the plans for extending identifiers to support Unicode?  How far
 are you willing to go?  ;)


I don't have any plans to support non-ascii characters for identifiers. The
unicode support is for strings and comments.


 I *really* want to be able to use the extra math symbols in Unicode as
 operators.  I could give you either a short list or a long list of the


ones

 I would want.  Just allowing any Unicode character that is considered a
 symbol or mathematical operator would be fine too.


That has a much more compelling case for it <g>.


 The ones that are most direly needed are

 dot product (U+22C5 although there are several similar symbols)
 cross product  (U+00D7)

 The reason we need these is that they're ultra common operations that have
 higher precedence than multiply, meaning none of the available


overloadable

 operators has the right precedence.

 but it'd also be nice to have:

 division operator (U+00F7)
 set union and intersection
 set membership
 logical operators (and, or, xor, nor, nand, not)
 comparison operators (single symbol support for <=, >=, !=, etc plus


"almost

 equal" for floats)
 single symbol support for <<, >>

 And I could go on and on.

 Sean

 ----- Original Message -----
 From: "Walter" <walter digitalmars.com>
 Newsgroups: D
 Sent: Wednesday, January 29, 2003 10:40 AM
 Subject: Re: Bug: Package names cannot start with digit.



 "Robert Medeiros" <robert.medeiros utoronto.ca> wrote in message
 news:b184a6$srp$1 digitaldaemon.com...

 As for the gothic 'R' notation: maybe if we get to the point where we




 can

 use UTF-?? for our source files... :)


 You can as of 0.51. But identifiers are still ascii.
Jan 30 2003
prev sibling parent reply "Sean L. Palmer" <seanpalmer directvinternet.com> writes:
"Robert Medeiros" <robert.medeiros utoronto.ca> wrote in message
news:b184a6$srp$1 digitaldaemon.com...

 Hi Sean,


 There's nothing particularly special about 3 dimensions anyway.  And 3D




or

 2D math and transformations certainly aren't limited in use to just
 graphics.  So I question the structure of your library.  Do you have a




2D

 mesh, or a 4D mesh?


 Actually, I invented that module name for illustration, but it was


prompted

 by an example from the library I'm working on. That's an implementation of
 the conformal model of geometric algebra, for a research project related


to

 computer vision. Some of the code is generic, i.e. applicable to blades


and

 multivectors of arbitrary dimension (for which I'm trying to apply D
 templates), but more often that not for my purposes I can get away with
 hand-crafted code for algebraic entities of fixed dimension (1 -> 5) which
 can be tweaked for efficiency, hence the 1d, 2d, etc. Your suggestion for
 using 'rN' notation is a good one that I think I'll adopt. Thanks!


Awesome!  I recently became very interested in geometric algebra and am
getting to the point of familiarity with it that I can write a multivector
class or write code that prints out all the individual adds and multiplies
involved in any arbitrary grade vs. grade product.  I've already made some
use of that stuff to optimize my quaternion transforming point function etc.

I think it's a great idea to make a geometric algebra template.  Have a look
at Boost::clifford  ( supposed to be at http://jaap.flipcode.com/ga/  but
seems down currently )   I would love to see what you come up with or even
help out with ideas or implementation.

In my C++ math library I use a graded system like you say, where mixing
different ranks together gives certain result types containing only the
nonzero portion of the resulting multivector.  Keeping track of which grades
are nonempty in a template would add complexity but would make it generate
really efficient code and storage.  There would be no real reason to have
special classes for points, vectors, and spinors, you could just use
multivector for everything.  That sounds ideal, but may require some
extensions to the existing template support to make it possible.

Once we have that, we would no longer need the complex type at all;  it
would subsume the role of quaternion, complex, and in fact most 3D
vector/plane/sphere/ray types wouldn't be necessary.


 As for the gothic 'R' notation: maybe if we get to the point where we can
 use UTF-?? for our source files... :)


Supposedly DMD 0.51 will read UTF-8 files as input but the lexer doesn't
like any characters outside the ascii range and will complain about them.
Being able to actually overload the cross product and dot product,
paragraph, dagger, left contraction symbols as operators would be fantastic!
The little superscript 2 could be Square, of course there's square root
symbol, ALL KINDS of good stuff in Unicode for what we need.  And it
wouldn't have to be hacks, provided the language supported those things
being overloaded.  Even if the precedence defaulted to the highest possible
it would still be light-years ahead of C++.


 Rob
Jan 30 2003
next sibling parent "Robert Medeiros" <robert.medeiros utoronto.ca> writes:
 Awesome!  I recently became very interested in geometric algebra and am
 getting to the point of familiarity with it that I can write a multivector
 class or write code that prints out all the individual adds and multiplies
 involved in any arbitrary grade vs. grade product.  I've already made some
 use of that stuff to optimize my quaternion transforming point function


etc.

I'm fairly recent to GA myself, only having discovered it this past summer.
It's fascinating stuff, isn't it? If you're like me at all, you probably
started reading, got mad that your grade school teachers didn't teach it
like that, and then became a True Believer, and started evangelizing to
friends, family, and strangers alike... :)


 I think it's a great idea to make a geometric algebra template.  Have a


look

 at Boost::clifford  ( supposed to be at http://jaap.flipcode.com/ga/  but
 seems down currently )   I would love to see what you come up with or even
 help out with ideas or implementation.


Thanks for the pointer -- I hadn't seen that page before; if you haven't
already visited:

http://carol.wins.uva.nl/~leo/clifford/

you might want to. It's a nice list of GA related resources. I'll be glad to
share the code once this project is a bit closer to completion. Actually,
I'm porting from a C++ codebase already written, and so some cycles are
getting spent just making things D-like, particularly rearranging code to
accomodate the notion of modules, sticking once separate unit tests into the
corresponding modules, etc. A fair amount of the design-work is done, but if
you have any suggestions for a better way to do things, well, I've rewritten
"finished" code a time or two before... :)


 In my C++ math library I use a graded system like you say, where mixing
 different ranks together gives certain result types containing only the
 nonzero portion of the resulting multivector.  Keeping track of which


grades

 are nonempty in a template would add complexity but would make it generate
 really efficient code and storage.  There would be no real reason to have
 special classes for points, vectors, and spinors, you could just use
 multivector for everything.  That sounds ideal, but may require some
 extensions to the existing template support to make it possible.


I was trying to avoid general multivector usage in favour of fixed-grade
elements for reasons of efficiency (it seemed wasteful to store all those
zero coefficients for a scalar, for instance), but I've recently started
thinking that maybe that's the wrong way to go about things. Perhaps it's
better to focus on making a high-quality, general multivector implementation
as you say (particularly if the template tracked the non-zero components as
you describe), getting more readable and maintainable code as a result, and
letting Moore deal with speed and storage concerns. I need to think about
this some more, but IIRC this is the way GABLE is implemented (a MATLAB
tutorial package for GA). Perhaps the added complexity of tracking zero
coefficients won't even be worth the storage gains, and where speed is a
concern it might be interesting to try mapping multivector operations onto
matrices to try getting a speed boost out of graphics hardware, at least for
Euclidean multivectors we use in graphics, computer vision, etc.


 Once we have that, we would no longer need the complex type at all;  it
 would subsume the role of quaternion, complex, and in fact most 3D
 vector/plane/sphere/ray types wouldn't be necessary.


<nod> I think 'complex' is nearing obsolescence. Of course, it won't really
go away until someone grows up having learned their maths without it, but we
can start by avoiding it ourselves I suppose. The transition might be made
easier by replacing complex with an equivalent bivector that behaves almost
identically, and leaving the more general multivector mechanism you describe
for those interested in the "new math". :) It would certainly be interesting
to have it defined as part of D, as the 'complex' type currently is. It
might be better though to leave it in Phobos/Deimos so different models of
GA can be accomodated without mandating a single standard. It seems that GA
software is still maturing; implementations still seem to be chasing a
running target as the mathmatics itself is still evolving at a fair clip,
relatively speaking.


 Supposedly DMD 0.51 will read UTF-8 files as input but the lexer doesn't
 like any characters outside the ascii range and will complain about them.
 Being able to actually overload the cross product and dot product,
 paragraph, dagger, left contraction symbols as operators would be


fantastic!

 The little superscript 2 could be Square, of course there's square root
 symbol, ALL KINDS of good stuff in Unicode for what we need.  And it
 wouldn't have to be hacks, provided the language supported those things
 being overloaded.  Even if the precedence defaulted to the highest


possible

 it would still be light-years ahead of C++.


I have to admit, I like the thought of being able to overload various
mathematical operators, and other symbols. The only difficulty I see is in
readability. As things stand, my preference for algebraic notation looks
like this (with some personal modifications tacked on):

http://www.cs.toronto.edu/~hehner/UA.pdf

and others are likely to use those same symbols for very different purposes.
'Seems as though we'd need to adopt new symbols into the language with a
canonical meaning, in the same way that '+' has a standard meaning, whose
function in well-designed software should be deducible from the context.

Rob
Jan 30 2003
prev sibling next sibling parent "Walter" <walter digitalmars.com> writes:
"Sean L. Palmer" <seanpalmer directvinternet.com> wrote in message
news:b1bs19$14ik$1 digitaldaemon.com...

 Supposedly DMD 0.51 will read UTF-8 files as input but the lexer doesn't
 like any characters outside the ascii range and will complain about them.


True. Reading the source text is just a starting point, at least so that
utf-16, etc., text editors can be used.


 Being able to actually overload the cross product and dot product,
 paragraph, dagger, left contraction symbols as operators would be


fantastic!

 The little superscript 2 could be Square, of course there's square root
 symbol, ALL KINDS of good stuff in Unicode for what we need.  And it
 wouldn't have to be hacks, provided the language supported those things
 being overloaded.  Even if the precedence defaulted to the highest


possible

 it would still be light-years ahead of C++.


It would probably have to be the highest precedence.
Jan 30 2003
prev sibling parent reply Farmer <itsFarmer. freenet.de> writes:
"Sean L. Palmer" <seanpalmer directvinternet.com> wrote in
news:b1bs19$14ik$1 digitaldaemon.com: 



 Supposedly DMD 0.51 will read UTF-8 files as input but the lexer
 doesn't like any characters outside the ascii range and will complain
 about them. Being able to actually overload the cross product and dot
 product, paragraph, dagger, left contraction symbols as operators
 would be fantastic! The little superscript 2 could be Square, of
 course there's square root symbol, ALL KINDS of good stuff in Unicode
 for what we need.  And it wouldn't have to be hacks, provided the
 language supported those things being overloaded.  Even if the
 precedence defaulted to the highest possible it would still be
 light-years ahead of C++. 


D would be light-years ahead of C++ ? 

Stroustrup thought about exploiting unicode for extended overloading in 
C++, almost five years ago.


B Stroustrup: Generalizing Overloading for C++2000. Overload, Issue 25. 
April 1, 1998 <g>
<http://www.research.att.com/~bs/whitespace98.pdf>   


Farmer.
Feb 02 2003
parent reply "Sean L. Palmer" <seanpalmer directvinternet.com> writes:
There's a big difference between "thought about it" and "implemented it".

Yeah, I guess that paper was an april fools joke.  But some of what's in
there could actually be worth pursuing.

Sean

"Farmer" <itsFarmer. freenet.de> wrote in message
news:Xns9316E669FBA21itsFarmer 63.105.9.61...

 D would be light-years ahead of C++ ?

 Stroustrup thought about exploiting unicode for extended overloading in
 C++, almost five years ago.


 B Stroustrup: Generalizing Overloading for C++2000. Overload, Issue 25.
 April 1, 1998 <g>
 <http://www.research.att.com/~bs/whitespace98.pdf>


 Farmer.
Feb 02 2003
parent "Daniel Yokomiso" <daniel_yokomiso yahoo.com.br> writes:
"Sean L. Palmer" <seanpalmer directvinternet.com> escreveu na mensagem
news:b1k70j$1fkr$1 digitaldaemon.com...

 There's a big difference between "thought about it" and "implemented it".

 Yeah, I guess that paper was an april fools joke.  But some of what's in
 there could actually be worth pursuing.

 Sean

 "Farmer" <itsFarmer. freenet.de> wrote in message
 news:Xns9316E669FBA21itsFarmer 63.105.9.61...

 D would be light-years ahead of C++ ?

 Stroustrup thought about exploiting unicode for extended overloading in
 C++, almost five years ago.


 B Stroustrup: Generalizing Overloading for C++2000. Overload, Issue 25.
 April 1, 1998 <g>
 <http://www.research.att.com/~bs/whitespace98.pdf>


 Farmer.




IIRC it was indeed a april fool's joke. If not it should, because in some
parts he talks about giving the default identifier name length to be just 1
character, and overload the "empty space" operator for ints to be
multiplication, so "x=yzw" is "x = y * z * w". I think the idea of using
unicode characters for certain operators would be a great idea for code
editing, but not for the language. It looks a good idea, but code is usually
linear, and I want to write e = mc2 with superscripting instead of lousy
power of operators ;-) The same goes for division or linear algebra. Maybe D
could always associate a operator with an operation, even for new operators,
and IDE's could make use of this:

// default operators
alias '+' add;
alias '*' mul;

// my module operators
alias "unicode for cross product goes here" cross;

or even allowing per-module aliasing of operators.




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