You are already doing exactly the right thing by having a temporary
variable.
To be precise a code fragment like:
(let [expensive-answer (some-fn x y z)
final-result { :k1 (f1 expensive-answer)
:k2 (f2 expensive-answer)
:k3 (f3 expensive-answer) } ]
final-result)
is already purely functional and very appropriate. In fact, there is even
a name for a closely-related technique:
https://refactoring.com/catalog/extractVariable.html
Alan
On Sat, May 13, 2017 at 1:26 PM, Kevin Kleinfelter <
kleinfelter.gro...@gmail.com> wrote:
> How would one convert the following procedural logic into
> functional/Clojure?
> x = expensive-calculation
> return (f1(x), f2(x), f3(x))
>
> I'm sure I could force it by using a var to save the intermediate value,
> but that's still procedural. It seems like the pattern of reusing an
> expensive result in multiple function calls without recalculating it must
> have a functional approach, but I'm not finding it.
>
> What I really want to do is to return:
> {:key1 f1(f0(x)), :key2 f2(f0(x)), :key3 f3(f0(x))}
>
> without paying the price of executing f0 multiple times.
>
> Tnx.
>
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