Hi,
Not really mechanisms, but two Idioms will help you with your problem:
Either wrap the defn in a let:
(let [U (gen-matrix [1 2 2 -2 -1 -2 2 2 3] 3 3)
A (gen-matrix [1 2 2 2 1 2 2 2 3] 3 3)
D (gen-matrix [-1 -2 -2 2 1 2 2 2 3] 3 3)
S (gen-vector [3 4 5])]
(letfn [(prims-from [m] [(mult m U) (mult m A) (mult m D)])
(next-prims [l] (flatten (map prims-from l)))]
(defn primitives
"Generates pythagorean primitives. Will filter them against
pred if
given."
([] (iterate next-prims [S]))
([pred] (iterate #(filter pred (next-prims %)) [S])))))
or use a default value for pred: (constantly true)
(defn primitives
"Generates pythagorean primitives. Will filter them against pred if
given."
([] (primitives (constantly true)))
([pred]
(let [U (gen-matrix [1 2 2 -2 -1 -2 2 2 3] 3 3)
A (gen-matrix [1 2 2 2 1 2 2 2 3] 3 3)
D (gen-matrix [-1 -2 -2 2 1 2 2 2 3] 3 3)
S (gen-vector [3 4 5])]
(letfn [(prims-from [m] [(mult m U) (mult m A) (mult m D)])
(next-prims [l] (flatten (map prims-from l)))]))
(iterate #(filter pred (next-prims %)) [S])))
The former will evaluate the values only once when the file is loaded
and keep them around until your program dies and do not impose any
runtime overhead when you call the function, because all variables are
already initialized.
The latter one uses a default argument to pred. (constantly true)
returns a n-argument function wich returns true on every invokation.
Erik
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