Hi all,
I was wondering if there was an idiomatic functional way to accomplish
the following:
We have some parameters, and we want to build a collection based on
those parameters. The collection could have as many as n items, and
whether and what items get added for each of the n possibilities will
depend on the parameters.
In Ruby, this might look like:
def build_coll(a, b)
coll = []
if a > 2
coll << (a * b)
end
if b > 2
coll << (a + b)
end
if a > b
coll << (a - b)
end
coll
end
build_coll(3, 1)
I'd like to accomplish this using a purely functional style. One way
to do this would be to reduce a collection of test functions with an
initial empty collection and a reduce function that adds the result of
the test element if the test passes:
(defn build-coll [a b]
(reduce
(fn [coll f] (if-let result (f a b) (conj coll result) coll))
[]
[(fn [a b] (if (> a 2) (* a b)))
(fn [a b] (if (> b 2) (+ a b)))
(fn [a b] (if (> a b) (- a b)))]))
(build-coll 3 1)
Does anyone have any better ideas about how to go about this?
Thanks,
- Mark McGranaghan
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