Data commit

Task/Evolutionary-algorithm/Smalltalk/evolutionary-algorithm-1.st

@@ -0,0 +1,47 @@
+String subclass: Mutant [
+    <shape: #character>
+
+    Target := Mutant from: 'METHINKS IT IS LIKE A WEASEL'.
+    Letters := ' ABCDEFGHIJKLMNOPQRSTUVWXYZ'.
+
+    Mutant class >> run: c rate: p
+        ["Run Evolutionary algorighm, using c copies and mutate rate p."
+        | pool parent |
+        parent := self newRandom.
+        pool := Array new: c+1.
+
+        [parent displayNl.
+        parent = Target] whileFalse:
+            [1 to: c do: [:i | pool at: i put: (parent copy mutate: p)].
+            pool at: c+1 put: parent.
+            parent := pool fold: [:winner :each | winner fittest: each]]]
+
+    Mutant class >> newRandom
+        [^(self new: Target size)
+            initializeToRandom;
+            yourself]
+
+    initializeToRandom
+        [self keys do: [:i | self at: i put: self randomLetter]]
+
+    mutate: p
+        [self keys do:
+            [:i |
+            Random next <= p ifTrue: [self at: i put: self randomLetter]]]
+
+    fitness
+        [| score |
+        score := 0.
+        self with: Target do:
+            [:me :you |
+            me = you ifTrue: [score := score + 1]].
+        ^score]
+
+    fittest: aMutant
+        [^self fitness > aMutant fitness
+            ifTrue: [self]
+            ifFalse: [aMutant]]
+
+    randomLetter
+        [^Letters at: (Random between: 1 and: Letters size)]
+]