Great stuff, and I like the use of a sentinel as a terminator symbol.
One aspect of this I would like to explore is that of a lazy sequence as a more
fundamental language primitive. Generators in for loops are great, but
generators returned by lapply() and friends would enable lazy functional
t
Thank you Lionel, Peter, and Duncan!
Some responses inline below:
> Couldn't this all be done in a while or repeat loop? ...
> Not as simple as yours, but I think a little clearer because it's more
> concrete, less abstract.
Indeed, that’s the trade-off! Explicit and verbose vs. simple,
concise,
Clever! If going for non-local returns, probably best for ergonomics to pass in
a closure (see e.g. `callCC()`). If only to avoid accidental jumps while
debugging.
But... do we need more lazy evaluation tricks in the language or fewer? It's
probably more idiomatic to express non-local returns with
Passing the sentinel value as an argument to the iteration method is
the approach taken in my package `iterors` on CRAN. If the sentinel
value argument is evaluated lazily, this lets you pass calls to things
like 'stop', 'break' or 'return,' which will be called to signal end
of iteration. This mak
Hello,
A couple of comments:
- Regarding the closure + sentinel approach, also implemented in coro
(https://github.com/r-lib/coro/blob/main/R/iterator.R), it's more
robust for the
sentinel to always be a temporary value. If you store the sentinel
in a list or
a namespace, it might inadverte
1. I'm not sure I see the need for the syntax change. Couldn't this all
be done in a while or repeat loop? E.g. your example could keep the
same definition of SampleSequence, then
iterator <- SampleSequence(2)
repeat {
sample <- iterator()
if (is.null(sample)) break
print(sample)
Hi all,
A while back, Hadley and I explored what an iteration protocol for R
might look like. We worked through motivations, design choices, and edge
cases, which we documented here:
https://github.com/t-kalinowski/r-iterator-ideas
At the end of this process, I put together a patch to R (with tes
