r - Custom Iterator with more than one return value -

my custom iterator bit slow. hope speed when use unlist(as.list(ic, n=2000)) construct. however, not know how implement functionality. found nextelem , hasnext methods. iterator looks this:

library(itertools) fibonacci <- function(count = na) {     ab = c(0, 1)     n <- function() {       if (!is.na(count)) {         if (count > 0) count <<- count -1         else stop('stopiteration')       }       #       ab <<- c(ab[2], sum(ab))       ab[1]     }     obj <- list(nextelem = n)     class(obj) <- c('fibonacci', 'abstractiter', 'iter')     obj } 

i can use this:

ic <- fibonacci () print (nextelem (ic)) 

now next 10 fibonacci numbers @ once, via

print(unlist(as.list(ic, n=10))) 

but of course needs implemented. how this?

the fibonacci iterator serves example. actually, work on iterator gives k-combinations of n-set, i.e. memory-friendly version of combn.