Question

I have a function that returns a map. The keys are static, but the values are conditional. Like this:

(defn map-returning-function [x y]
  {:a (if (some-test-fn x)  "one value" "other value"
   :b (if (some-test-fn x)   15         25
   :c (if (different-test y) :one       :two})

Is there some more elegant way to achieve this without needing to write the if test for each value? The only other way I can think of is

(defn another-map-returning-function [x y]
  (if (some-test-fn x)
    {:a "one value",  :b 15, :c (if (different-test y) :one :two)}
    {:a "other value" :b 25, :c (if (different-test y) :one :two)}))

which doesn’t seem much better to me since it repeats the key names for each branch of the conditional and it repeats of the function call on different-test. And heaven forbid that I need a cond instead of just an if.

Answer 1

How about this:

(let [test-x (some-test x) test-y (some-test y)] 
  (conj 
    (if test-x {:a "one value" :b 15} {:a "other value" :b 25}) 
    (if test-y {:c :one} {:c :two})))

Conditions executed once and in one place, then used in another. Depends on context and personal preference though. Something more like your example may be cleaner:

(let [test-x (some-test x) test-y (some-test y)] 
  {:a (if test-x "one value" "other value")
   :b (if test-x 15 25)
   :c (if test-y :one :two)})