On 29/10/2008 4:39 PM, Alexy Khrabrov wrote:
I found there's a very good functional set of operations in R, such as
apply family, Hadley Wickham's lovely plyr, etc. There's even a
Reduce (a.k.a. fold). Now I wonder how can we do pattern-matching?
E.g., now I split dimensions like this:
m <- dim(V)[1] # R
n <- dim(V)[2] # still R
While even Matlab allows for
[m,n] = size(V) % MATLAB!
Ideally I'd be able to say,
<<x,y>> <- dim(V)
-- where <<.,.>> is some magic needed.
Similarly, to break lists, we'd need, in a MLish notation,
match L with
| head::tail => ...
| () => ;
What can be done in R now to simulate it, and/or how Rish is it to add
something like that?
You can do this:
names <- c("m", "n")
for (i in seq_along(names)) assign(names[i], dim(V)[i])
With some trickery, I think you could write a function that did this
based on syntax like
_(m, n) <- dim(V)
I would call this quite non-Rish. It needs tricky evaluation (m and n
are only there as names, not as bindings to objects).
I don't know ML, so I don't understand your second example.
Duncan Murdoch
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