From m@||und @end|ng |rom b|rc@@u@dk  Sat May 25 07:40:46 2019
From: m@||und @end|ng |rom b|rc@@u@dk (Thomas Mailund)
Date: Sat, 25 May 2019 05:40:46 +0000
Subject: [Rd] 
 Give update.formula() an option not to simplify or reorder the
 result -- request for comments
In-Reply-To: <CAB8pepy_OJyxZNJMm=_GXQrcpYT0dXz22QrCCU0tSo+GRVEL1A@mail.gmail.com>
References: <56ee72cb833f01d6eb3925452925d54f7c2e03d7.camel@uow.edu.au>
 <CAB8pepy_OJyxZNJMm=_GXQrcpYT0dXz22QrCCU0tSo+GRVEL1A@mail.gmail.com>
Message-ID: <etPan.5ce8d55a.6d9d6b7e.123@uni.au.dk>

With a bit of meta programming that manipulates expressions, I don?t think this would be difficult to implement in a package. Well, as difficult as it is to implement a CAS, but not harder. I wrote some code for symbolic differentiation ? I don?t remember where I put it ? and that was easy. But that is because differentiation is just a handful of rules and then the chain rule. I don?t have the skills for handling more complex symbolic manipulation, but anyone who could add it to the language could also easily add it as a package, I think.

Whether in a standard package or not, I have no preference whatsoever.

Cheers
Thomas



On 25 May 2019 at 00.59.44, Abby Spurdle (spurdle.a at gmail.com<mailto:spurdle.a at gmail.com>) wrote:

> Martin Maechler has asked me to send this to R-devel for discussion
> after I submitted it as an enhancement request (
> https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17563).

I think R needs to provide more support for CAS-style symbolic computation.
That is, support by either the R language itself or the standard packages,
or both.
(And certainly not by interfacing with another interpreted language).

Obviously, I don't speak for R Core.
However, this is how I would like to see R move in the future.
...improved symbolic and symbolic-numeric computation...

I think any changes to formula objects or their methods, should be
congruent with these symbolic improvements.

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[Rd] Give update.formula() an option not to simplify or reorder the result -- request for comments
Thomas Mailund