I have a number of fairly nasty functions with a form that looks like
this:
(defn default-ontology
([f]
(dispatch f))
([f a]
(dispatch f a))
([f a b]
(dispatch f a b))
([f a b c]
(dispatch f a b c))
([f a b c d]
(dispatch f a b c d))
([f a b c d e]
(dispatch f a b c d e))
([f a b c d e fa]
(dispatch f a b c d e fa))
([f a b c d e fa g]
(dispatch f a b c d e fa g))
([f a b c d e fa g h]
(dispatch f a b c d e fa g h))
([f a b c d e fa g h i]
(dispatch f a b c d e fa g h i))
([f a b c d e fa g h i j]
(dispatch f a b c d e fa g h i j)))
The reason for all of this is that I need to avoid the use of variadic
function calls for performance reasons -- this function gets called a
lot in my code base, and without this unwinding, I box and unbox
consistantly.
Now, I dislike the code repetition here, and indeed have found already
found one bug in my code where I missed a variable out, something like....
([f a b c d]
(dispatch f a b d))
which is hard to pick up on.
I can't make the whole thing a macro because I need to pass this as a
first class function. And I can't macro each of the variadic elements
since the I'd need to return two elements at once.
The best I have done up with so far is:
(defn ^:private form-with-arity[n]
;; left as an exercise for the reader
)
(defmacro ^:private m-default-ontology
`(defn default-ontology
~@(map form-with-arity (range 1 10))))
(m-default-ontology)
Or am I missing something more obvious?
Phil
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