Background: I'm implementing a heuristic search over a tree of
possibilities. The heuristic calculation runs over a map of state. I have a
large number of nested functions that support this heuristic. So, for
convenience, I often pass around `state` as the first argument in these
functions. Inside, I use the :keys destructuring style.
Commentary: This approach is convenient; however, I feel like I've veered
towards one of the pitfalls of OO programming, where this "convenient"
composition of data hides the essence of the problem. In contrast, in other
projects, I've done lots of memoization -- this is easy when all arguments
are explicit.
Questions: Have others faced this tradeoff? How do you think about it? How
do you strike a balance, if there is one? More pointedly, is there a way to
get the best of both worlds (e.g. the "composed" argument style AND
memoization)?
Possible Solution: What about writing a macro to help? It would not be hard
to handle the memoization of some 'base-level' functions:
(defn f1 [{:keys [a b] :as state}] :costly-calculation-of-a-b)
(defn f2 [{:keys [b c] :as state}] :costly-calculation-of-b-c)
However, when it comes to a chain of functions, the memoization is not
apparent:
(defn f3 [{:keys [x] :as state}] (+ (f1 state) (f2 state) (g x)))
In order to memoize `f3`, one would need to account for not only `x` but
also `a`, `b`, and `c`. This would be an improvement over memoizing the
entire state.
Any thoughts on this kind of solution? Has it already been done? Are there
other, possibly better, ways to address this overall challenge?
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