combining mathematical notation and value substitution
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.