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m-lift as a function (m-lift-fn) #2

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65169fe
m-lift-fn
Sgeo Aug 25, 2012
cd8cec1
m-lift-fn change and test
Sgeo Sep 15, 2012
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11 changes: 11 additions & 0 deletions src/main/clojure/clojure/algo/monads.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -267,6 +267,17 @@
(m-result '())
(reverse ms)))

(defmonadfn m-lift-fn
"A purely functional replacement for m-lift
((m-lift 2 +) (m-result 5) (m-result 6)) should be equal to
((m-lift-fn +) (m-result 5) (m-result-6))
Note that this is untested"
[f]
(fn [& args]
(m-bind
(m-seq args)
#(m-result (apply f %)))))

(defmonadfn m-map
"'Executes' the sequence of monadic values resulting from mapping
f onto the values xs. f must return a monadic value."
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18 changes: 17 additions & 1 deletion src/test/clojure/clojure/algo/test_monads.clj
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Expand Up @@ -12,7 +12,7 @@
(:use [clojure.test :only (deftest is are run-tests)]
[clojure.algo.monads
:only (with-monad domonad m-lift m-seq m-chain writer-m write
sequence-m maybe-m state-m maybe-t sequence-t)]))
sequence-m maybe-m state-m maybe-t sequence-t m-lift-fn)]))


(deftest domonad-if-then
Expand Down Expand Up @@ -95,6 +95,22 @@
'(0 0 0 1 0 0 1 0 1 2)
(m-plus (range 3) (range 2))
'(0 1 2 0 1))))

(deftest sequence-monad-using-m-lift-fn
(with-monad sequence-m
(are [a b] (= a b)
(domonad [x (range 3) y (range 2)] (+ x y))
'(0 1 1 2 2 3)
(domonad [x (range 5) y (range (+ 1 x)) :when (= (+ x y) 2)] (list x y))
'((1 1) (2 0))
((m-lift-fn #(list %1 %2)) (range 3) (range 2))
'((0 0) (0 1) (1 0) (1 1) (2 0) (2 1))
(m-seq (replicate 3 (range 2)))
'((0 0 0) (0 0 1) (0 1 0) (0 1 1) (1 0 0) (1 0 1) (1 1 0) (1 1 1))
((m-chain (replicate 3 range)) 5)
'(0 0 0 1 0 0 1 0 1 2)
(m-plus (range 3) (range 2))
'(0 1 2 0 1))))

(deftest maybe-monad
(with-monad maybe-m
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