День третий (an investigation)

TASK
An Investigation. R and tail recursion. Lazy evaluation in R.

SOLUTION
With a Google's help i found this message: http://finzi.psych.upenn.edu/R/Rhelp02a/archive/73651.html
> Some functional languages have a feature called tail recursion that
> can provide performance improvements if you write your recursions
> to take advantage of it:
>
> http://en.wikipedia.org/wiki/Tail_recursion
>
> but I don't think R supports it. Is this likely to become available
> in R?
No. For a start, this is usually done by compilers, which we don't got.
In addition, it would be very difficult to do tail recursion optimization and not break most of the sys.* functions, which give explicit access to all the frames that would be optimized away.
-thomas

Alas, R doesn't have tail recursion optimization. That explains last error messages about stack fault. Now, what do they mean, when they write: "R is a functional language, with lazy evaluation"?
Here is the answer:

http://tolstoy.newcastle.edu.au/R/help/03b/0731.html
"...R is a functional language, with lazy evaluation and weak dynamic typing (a variable can change type at will: a <- 1 ; a <- "a" is allowed). Semantically, everything is copy-on-modify although some optimization tricks are used in the implementation to avoid the worst inefficiencies. Parameter passing is according to the "pass-by-value illusion", i.e. what is really getting passed down to a function is a "promise", which embodies the expression used in the call. This is at the core of the lazy evaluation mechanism: The result of the expression is not computed until needed. It also allows a function to get hold of the the expression itself: This is useful for labeling plots but it also allows some variants of "pass-by-name"-like semantics via evaluation in the environment of the caller..."

But... Extra!Extra! I found more sensational materials...
"Besides lazy evaluation in R is not really lazy evaluation!" http://www.postech.ac.kr/~gla/paper/R-ism-dec-8.ppt

CONCLUSIONS
So, my first impression, when i started this blog, was: "Incredibly! Such perfect program for data analysis, visualization, uses functional language." Now i see, R is not perfect.