[R] combining mathematical notation and value substitution

[Faheem Mitha]

On Sat, 21 Jun 2003, Uwe Ligges wrote:

> Faheem Mitha wrote:

> > Can you go into a little more detail here about why alpha here is a
> > call?
>
> Thomas already told it and ?expression says as well: "expression returns
> a vector of mode "expression" containing its arguments as unevaluated
> ``calls''."

Yes, but it is just a call by definition then? If you put anything in the
place of alpha it would be a call?

>  > I'm not terribly clear what a call is. If it so similar to an
> > expression, what distinguishes it from an expression, and why do we
> > need two similar concepts like this?
>
> Obviously a question for Bill Venables. I admit I've not thought about
> it before. In this context the article
>   W. N. Venables (2002). Programmer’s Niche, R News, 2(2): 24–26,
>   ISSN 1609-3631, http://CRAN. R-project.org/doc/Rnews/,
> and
>   Venables & Ripley (2000): S Programming, Springer.
> are nice references.

I've got "S Programming" and spent some of yesterday reading it. It
doesn't go into detail into the difference between expressions and calls.
It does have a table on pg 66 which gives examples of different modes.

                                                           Faheem.