I'm trying to make a functional version of minmax algorithm as shown
in John Hughes Why functional programming matters? work [http://
www.scribd.com/doc/26902/whyfp].
I'm hitting problems when applying maximise function on my gametree.
For some reason the maximise call won't return the best value the
position can get but a nested list of numbers. Like the call to min/
max functions is not done at all. The results nesting depends on the
given search depth. For depth 2 it returns list of list of numbers.
What am I doing wrong here? As far as I know the maximise / minimise
functions should return one integer, not a list in any case?
Here's my version of the maximise / minimise functions, haskell
version in comments:
;; maximise (node n nil) = n
;; maximise (node n sub) = max (map minimise sub)
(declare minimise)
(defn- maximise [node]
(if (empty? (:subtree node))
(:label node)
(max (map minimise (:subtree node)))))
;; minimise (node n nil) = n
;; minimise (node n sub) = min (map maximise sub)
(defn- minimise [node]
(if (empty? (:subtree node))
(:label node)
(min (map maximise (:subtree node)))))
;; evaluate = maximise . maptree static . prune 5 . gametree
(defn evaluate-minmax [depth state]
(do (println "###")
(print "EVALUATE-MINMAX[depth state]:")
(prn depth state)
(println "###")
(let [tree (->> state
gametree
(prune depth)
(maptree static))]
(do (println "###")
(print "Calling maximise on tree:")
(prn tree)
(println "###")
(maximise tree)))))
### And output of the maximise call ###
###
Calling maximise on tree:#:tursas.search2.Node{:label 21, :subtree
(#:tursas.search2.Node{:label 79, :subtree
(#:tursas.search2.Node{:label 4, :subtree nil}
#:tursas.search2.Node{:label 76, :subtree nil}
#:tursas.search2.Node{:label 82, :subtree nil}
#:tursas.search2.Node{:label 82, :subtree nil}
#:tursas.search2.Node{:label 67, :subtree nil}
#:tursas.search2.Node{:label 30, :subtree nil}
#:tursas.search2.Node{:label 94, :subtree nil}
#:tursas.search2.Node{:label 70, :subtree nil}
#:tursas.search2.Node{:label 82, :subtree nil}
#:tursas.search2.Node{:label 84, :subtree nil}
#:tursas.search2.Node{:label 54, :subtree nil}
#:tursas.search2.Node{:label 29, :subtree nil})}
#:tursas.search2.Node{:label 8, :subtree (#:tursas.search2.Node{:label
38, :subtree nil} #:tursas.search2.Node{:label 47, :subtree nil}
#:tursas.search2.Node{:label 65, :subtree nil}
#:tursas.search2.Node{:label 32, :subtree nil}
#:tursas.search2.Node{:label 88, :subtree nil}
#:tursas.search2.Node{:label 20, :subtree nil}
#:tursas.search2.Node{:label 21, :subtree nil}
#:tursas.search2.Node{:label 37, :subtree nil}
#:tursas.search2.Node{:label 93, :subtree nil}
#:tursas.search2.Node{:label 88, :subtree nil}
#:tursas.search2.Node{:label 78, :subtree nil}
#:tursas.search2.Node{:label 66, :subtree nil})}
#:tursas.search2.Node{:label 34, :subtree
(#:tursas.search2.Node{:label 42, :subtree nil}
#:tursas.search2.Node{:label 56, :subtree nil}
#:tursas.search2.Node{:label 72, :subtree nil}
#:tursas.search2.Node{:label 55, :subtree nil}
#:tursas.search2.Node{:label 29, :subtree nil}
#:tursas.search2.Node{:label 79, :subtree nil}
#:tursas.search2.Node{:label 86, :subtree nil}
#:tursas.search2.Node{:label 30, :subtree nil}
#:tursas.search2.Node{:label 74, :subtree nil}
#:tursas.search2.Node{:label 87, :subtree nil}
#:tursas.search2.Node{:label 58, :subtree nil}
#:tursas.search2.Node{:label 84, :subtree nil})}
#:tursas.search2.Node{:label 78, :subtree
(#:tursas.search2.Node{:label 69, :subtree nil}
#:tursas.search2.Node{:label 41, :subtree nil}
#:tursas.search2.Node{:label 69, :subtree nil}
#:tursas.search2.Node{:label 34, :subtree nil}
#:tursas.search2.Node{:label 30, :subtree nil}
#:tursas.search2.Node{:label 42, :subtree nil}
#:tursas.search2.Node{:label 12, :subtree nil}
#:tursas.search2.Node{:label 34, :subtree nil}
#:tursas.search2.Node{:label 22, :subtree nil}
#:tursas.search2.Node{:label 46, :subtree nil}
#:tursas.search2.Node{:label 67, :subtree nil}
#:tursas.search2.Node{:label 16, :subtree nil})}
#:tursas.search2.Node{:label 61, :subtree
(#:tursas.search2.Node{:label 52, :subtree nil}
#:tursas.search2.Node{:label 84, :subtree nil}
#:tursas.search2.Node{:label 84, :subtree nil}
#:tursas.search2.Node{:label 65, :subtree nil}
#:tursas.search2.Node{:label 30, :subtree nil}
#:tursas.search2.Node{:label 75, :subtree nil}
#:tursas.search2.Node{:label 57, :subtree nil}
#:tursas.search2.Node{:label 87, :subtree nil}
#:tursas.search2.Node{:label 96, :subtree nil})}
#:tursas.search2.Node{:label 39, :subtree
(#:tursas.search2.Node{:label 39, :subtree nil}
#:tursas.search2.Node{:label 34, :subtree nil}
#:tursas.search2.Node{:label 77, :subtree nil}
#:tursas.search2.Node{:label 56, :subtree nil}
#:tursas.search2.Node{:label 30, :subtree nil}
#:tursas.search2.Node{:label 16, :subtree nil}
#:tursas.search2.Node{:label 95, :subtree nil}
#:tursas.search2.Node{:label 96, :subtree nil}
#:tursas.search2.Node{:label 84, :subtree nil}
#:tursas.search2.Node{:label 51, :subtree nil}
#:tursas.search2.Node{:label 58, :subtree nil}
#:tursas.search2.Node{:label 94, :subtree nil})})}
###
((4 76 82 82 67 30 94 70 82 84 54 29) (38 47 65 32 88 20 21 37 93 88
78 66) (42 56 72 55 29 79 86 30 74 87 58 84) (69 41 69 34 30 42 12 34
22 46 67 16) (52 84 84 65 30 75 57 87 96) (39 34 77 56 30 16 95 96 84
51 58 94))
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