Integrate with magrittr

[ramhiser]

Iterators and itertools2 will be more flexible and useful if they can be used with magrittr pipes (and ultimately with dplyr). It turns out that pipes do, in fact, work in some cases.

Example (related to #41):

as_vector <- function(x) {
  unlist(as.list(x))
}

set.seed(42)
irep(function(x) rnorm(1), times=10) %>% as_vector
# [1]  1.37095845 -0.56469817  0.36312841  0.63286260  0.40426832 -0.10612452  1.51152200 -0.09465904
# [9]  2.01842371 -0.06271410

Next Steps

• Construct lots of use cases where pipes are used.
• Lots of unit tests based on these examples.

[ramhiser]

A good motivating example:

person = c( 'Grace', 'Grace', 'Grace', 'Rob', 'Rob', 'Rob' )
foods   = c( 'apple', 'banana', 'cucumber', 'spaghetti', 'cucumber', 'banana' )
eaten <- data_frame(person, foods)

eaten %>% group_by(person) %>% do(function(x) combn(x$foods, m = 2))