François Pinard wrote:
> [Roland Rau]
>
>> [François Pinard]
>>
>
>
>>> I wonder what happened, for R to hide the underlying Scheme so fully,
>>> at least at the level of the surface language (despite there are
>>> hints).
>>>
>
>
>> "To further foster portability, we chose to write R in ANSI C...."
>>
>
> Yes, of course. Scheme is also (often) implemented in C. I meant that
> R might have implemented a Scheme engine (or part of a Scheme engine,
> extended with appropriate data types) with a surface language (nearly
> the S language) which is purposely not Scheme, but could have been.
>
> If the gap is not extreme, one could dare dreaming that the Scheme
> engine in R be "completed", and Scheme offered as an alternate extension
> language. If you allow me to continue dreaming awake -- "they" told me
> "they" will let me free as long as I do not get dangerous! :-) -- part
> of the interest lies in the fact there are excellent Scheme compilers.
> If we could only find or devise some kind of marriage between a mature
> Scheme and R, so to speed up the non-vectorisable parts of R scripts...
>
>
Well, depending on what you want, this is either trivial or
impossible... The internal storage of R is still pretty much equivalent
to scheme. E.g. try this:
> r2scheme <- function(e) if (!is.recursive(e))
deparse(e) else c("(", unlist(lapply(as.list(e), r2scheme)), ")")
> paste(r2scheme(quote(for(i in 1:4)print(i))), collapse=" ")
[1] "( for i ( : 1 4 ) ( print i ) )"
and a parser that parses a similar language to R internal format is not
a very hard exercise (some care needed in places). However, replacing
the front-end is not going to make anything faster, and the evaluation
engine in R does a couple of tricks which are not done in Scheme,
notably lazy evaluation, and other forms of non-local evaluation, which
drives optimizers crazy. Look up the writings of Luke Tierney on the
matter to learn more.
>> If we are lucky and one of the original authors reads this thread they
>> might explain the situation further and better [...].
>>
>
> In r-devel, maybe! We would be lucky if the authors really had time to
> read r-help. :-)
>
>
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