https://github.com/aengelberg/clj-generators
My all-time favorite feature of Python is "generators." It allows you to
write lazy sequences imperatively.
def infinite_range():
x = 1
while True:
yield x
x += 1
for i in infinite_range():
if (i > 5):
break
else:
print(i)
=> 1 2 3 4 5
This feature is so amazing and powerful, a common practice of mine is to
ponder how to implement such magic in other languages. Python implements
this feature using virtual stacks to suspend the computation in memory.
Most languages don't have a similar way to "pause" a computation like that,
short of manipulating entire threads, which gets messy quickly. However,
when core.async came out for Clojure, I realized that the go-blocks can in
fact "pause" in a lightweight way (because they "park" as they read/write),
so it came to mind as a possible candidate for a Python generator
implementation. The infinite_range example above would translate to the
following Clojure code:
(defn infinite-range []
(generator
(loop [x 1]
(yield x)
(recur (inc x)))))
(take 5 (infinite-range))
=> (1 2 3 4 5)
I realize this is a bit more imperative than most Clojure programmers would
like. However, the addition of generators allows functional macros like
"loop" to create lazy sequences (like in the example above), which it
previously was unable to do.
Check out the github site <https://github.com/aengelberg/clj-generators>
for more details. It's relatively slow and inefficient but serves as a
proof-of-concept. Enjoy!
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