Expression Parser

Expression Parser

[Ehud Lamm]

Does anyone know of simple embeddable exprssion parser that I can reuse?
Ideally should support numeric as well as string data, and if constructs.

Thanks. 

Ehud Lamm     mslamm@pluto.mscc.huji.ac.il
http://purl.oclc.org/NET/ehudlamm  <== My home on the web

Re: Expression Parser

[Jeffrey D. Cherry]

Although it's not a parser, a good place to start would be the OpenToken
page:

   http://www.telepath.com/dennison/Ted/OpenToken/OpenToken.html

From the code and examples available at this site, you may find that
with a little code of your own, it's all you really need.  Hope this
helps!

-- 
Regards,
Jeffrey D. Cherry
Senior IV&V Analyst
Logicon Space and Information Operations
Logicon Inc.
a Northrop Grumman company

Re: Expression Parser

[Brian Rogoff]

On Tue, 27 Jul 1999, Ehud Lamm wrote:
> Does anyone know of simple embeddable exprssion parser that I can reuse?
> Ideally should support numeric as well as string data, and if constructs.

John English's excellent Ada intro uses an expression parser as one of his 
examples, and the code seemed easy to pick through IMO. The code is on
his web page. http://www.it.bton.ac.uk/je/adacraft/. 

If its truly simple as you say then recursive descent is a quick enough 
way to code it up, and contrary to popular opinion, can certainly handle
some grammars that are not LL(1). 

-- Brian  

Re: Expression Parser

[Ehud Lamm]

On Wed, 28 Jul 1999, Jeffrey D. Cherry wrote:

|Although it's not a parser, a good place to start would be the OpenToken
|page:
|
| http://www.telepath.com/dennison/Ted/OpenToken/OpenToken.html
|

Since it seems I'll have to hack something up myself, I'll give this a
clsoe look. From what i've seen it seems very nice.

I'll take this opportunity to share an observation. Ada is designed for
reuse and for good SE practices. Since the latter discourage many would be
Ada hackers, we end up with less code to reuse.
Of course bad code shouldn't be reused, but the more code out there the
greater the chance some of it will be good.

I checked out a site dedicated to Lego_Mindstorms
(http://www.crynwr.com/lego-robotics/) and didn't see any Ada interface.
If someone is interested in this sort of thing, this seems like a fun
project.

Ehud Lamm     mslamm@pluto.mscc.huji.ac.il
http://purl.oclc.org/NET/ehudlamm  <== My home on the web
 

Re: Expression Parser

[Gautier]

2 examples in Pascal:

http://www.autosci.com/sample.txt
http://atlas.csd.net/~cgadd/knowbase/MATH0050.HTM

-- 
Gautier

--------
http://members.xoom.com/gdemont/

Re: Expression Parser

[Martin C. Carlisle]

In article <Pine.A41.3.96-heb-2.07.990729112145.104782E-100000@pluto.mscc.huji.ac.il>,
Ehud Lamm  <mslamm@mscc.huji.ac.il> wrote:
>On Wed, 28 Jul 1999, Jeffrey D. Cherry wrote:
>I checked out a site dedicated to Lego_Mindstorms
>(http://www.crynwr.com/lego-robotics/) and didn't see any Ada interface.
>If someone is interested in this sort of thing, this seems like a fun
>project.

We are exploring this possibility at the Air Force Academy.  I am not the lead
on this, but am giving some technical advice.

--Martin


-- 
Martin C. Carlisle, Asst Prof of Computer Science, US Air Force Academy
carlislem@acm.org, http://www.usafa.af.mil/dfcs/bios/carlisle.html
DISCLAIMER:  This content in no way reflects the opinions, standards or 
policy of the US Air Force Academy or the United States Government.

Re: Expression Parser

[Ehud Lamm]

On Thu, 29 Jul 1999, Brian Rogoff wrote:

|John English's excellent Ada intro uses an expression parser as one of his 
|examples, and the code seemed easy to pick through IMO. The code is on
|his web page. http://www.it.bton.ac.uk/je/adacraft/. 

Hi,

I already checked his parser, in chapter 17. But I think I like your
second option better.

|If its truly simple as you say then recursive descent is a quick enough 
|way to code it up, and contrary to popular opinion, can certainly handle
|some grammars that are not LL(1). 

Quite. As I said in my previous posts, or at least I think I said it - it
seems I'll hack a recursive decent parser myself. Won't be the first time.
In many cases it is faster to do that than use a parser generator, even
when there are tons that float arround.

Ehud Lamm     mslamm@pluto.mscc.huji.ac.il
http://purl.oclc.org/NET/ehudlamm  <== My home on the web

Re: Expression Parser

[Ted Dennison]

In article
<Pine.A41.3.96-heb-2.07.990729112145.104782E-100000@pluto.mscc.huji.ac.i
l>,
  Ehud Lamm <mslamm@mscc.huji.ac.il> wrote:
> On Wed, 28 Jul 1999, Jeffrey D. Cherry wrote:
>
> |Although it's not a parser, a good place to start would be the
OpenToken
> |page:
> |
> | http://www.telepath.com/dennison/Ted/OpenToken/OpenToken.html
> |
>
> Since it seems I'll have to hack something up myself, I'll give this a
> clsoe look. From what i've seen it seems very nice.

I have used it for several different tasks here at work, and have found
it quite handy. But if there's something you could use that it doesn't
do very well, please tell me. That goes for documentation as well. Now
that my summer class is ending, I should have more time to devote to
developing it.

Parsing capability *will* be added in a future version.

Wow. This would come up on the week I took off to work on my AI project.
:-(

> I'll take this opportunity to share an observation. Ada is designed
> for reuse and for good SE practices. Since the latter discourage many
> would be Ada hackers, we end up with less code to reuse.
> Of course bad code shouldn't be reused, but the more code out there
> the greater the chance some of it will be good.

I don't really think that's entirely accurate. I figure there just
aren't as many folks around who know Ada. Considering that, there really
are a great deal of reusable Ada packages floating around. If anything,
I'd say the language encourages it *more* than C, because it is much
more portable.

For instance, as part of my AI project I gave a go at porting the
open-source game Empire to cygwin32. It already has #ifdef's and make
rules in to support gcc on several Unix platforms and MSVC++. So both
the compiler and the platform were already supported, just not together.
After 8 hours of work on a Saturday that could have been much better
spent playing with my kids, I finally gave up the ghost. I ended up
having to hack it into a DLL so I could link it with Gnat.

OpenToken, on the other hand, compiles as-is with no source changes on
at least 3 different Ada compilers using 2 different OS'es that I know
of. I have yet to receive a report of a portability problem.

Its really sad to think of the amount of effort the world wastes in C
porting...

--
T.E.D.


Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't.

Re: Expression Parser

[David Botton]

I would like to point out that to my understanding there is a COM (aka
ActiveX) interface available for the Lego_Mindstorms product.

Therefore you can use it from Ada by just running BindCOM
(http://www.adapower.com/com) on the COM object to produce a thick and thin
Ada binding to it.

Of course if any one wants to send me one, I'll test it for you :)

David Botton

Martin C. Carlisle wrote in message <7npml7$9iu$1@cnn.Princeton.EDU>...
>In article
<Pine.A41.3.96-heb-2.07.990729112145.104782E-100000@pluto.mscc.huji.ac.il>,
>Ehud Lamm  <mslamm@mscc.huji.ac.il> wrote:
>>On Wed, 28 Jul 1999, Jeffrey D. Cherry wrote:
>>I checked out a site dedicated to Lego_Mindstorms
>>(http://www.crynwr.com/lego-robotics/) and didn't see any Ada interface.
>>If someone is interested in this sort of thing, this seems like a fun
>>project.
>
>We are exploring this possibility at the Air Force Academy.  I am not the
lead
>on this, but am giving some technical advice.
>
>--Martin
>

Re: Expression Parser

[Ehud Lamm]

On Sat, 31 Jul 1999, David Botton wrote:

|I would like to point out that to my understanding there is a COM (aka
|ActiveX) interface available for the Lego_Mindstorms product.
|
|Therefore you can use it from Ada by just running BindCOM
|(http://www.adapower.com/com) on the COM object to produce a thick and thin
|Ada binding to it.

Sounds real nice. But points to another thing. Notice how beginners have a
hard time  with Ada? How often do we hear questions like "I am starting
with Ada, how do I..."? 

Having a good platform for starting out is crucial for language success
(in the hobby market at least), recall Turbo Pascal, BASICA/QBASIC etc
etc.

GNAT is great, but packaging it with mroe examples etc. esp. with easier
to understand Windows examples, and perhaps a GUI builder will help
greatly. Supplying a standard library of data structures and algorithms,
with examples of use will also be a step in the right direction.

Another idea is evloving something like PERL's CPAN. The Source Code
Treasury seems like a very good starting point.

This can be an intersting thesis work - infrastructure for reuse and
collaboration of programming language resources on the Internet.

Ehud Lamm     mslamm@pluto.mscc.huji.ac.il
http://purl.oclc.org/NET/ehudlamm  <== My home on the web

Re: Expression Parser

[David C. Hoos, Sr.]

Ehud Lamm wrote in message ...
<snip>
>Another idea is evloving something like PERL's CPAN. The Source Code
>Treasury seems like a very good starting point.
>
Speaking of Perl... I also had a need for an expression parser in an
Ada program.  After looking at what's available, and the time it
would take to do what I need in Ada, I decided on embedding a Perl
interpreter.

I spent one day developing the package, and the test program, and
testing the interpreter.

You might want to consider such an approach.

David C, Hoos, Sr.

Re: Expression Parser

[David Botton]

Is the package available for public consumption?

David Botton

David C. Hoos, Sr. wrote in message <7o7o47$91c@hobbes.crc.com>...

>Speaking of Perl... I also had a need for an expression parser in an
>Ada program.  After looking at what's available, and the time it
>would take to do what I need in Ada, I decided on embedding a Perl
>interpreter.

Re: Expression Parser

[David C. Hoos, Sr.]

David Botton wrote in message <7oatq8$1fp6$1@news.gate.net>...
>Is the package available for public consumption?
>
>David Botton
>
>David C. Hoos, Sr. wrote in message <7o7o47$91c@hobbes.crc.com>...
>
>>Speaking of Perl... I also had a need for an expression parser in an
>>Ada program.  After looking at what's available, and the time it
>>would take to do what I need in Ada, I decided on embedding a Perl
>>interpreter.


I'll try to make it available this weekend.  In its present form it
depends on my development environment (Makefiles, etc.) to be useful.
I also need to write a README file.

Re: Expression Parser

[Samuel Tardieu]

>>>>> "David" == David C Hoos, <david.c.hoos.sr@ada95.com> writes:

David> Speaking of Perl... I also had a need for an expression parser
David> in an Ada program.  After looking at what's available, and the
David> time it would take to do what I need in Ada, I decided on
David> embedding a Perl interpreter.

Well, it would have probably been simpler to interface with the PCRE
library (Perl Compatible Regular Expressions).

  Sam
-- 
Samuel Tardieu -- sam@ada.eu.org