September 2017 Update

Task/Evolutionary-algorithm/Zkl/evolutionary-algorithm.zkl

@@ -0,0 +1,14 @@
+const target = "METHINKS IT IS LIKE A WEASEL";
+const C = 100;  // Number of children in each generation.
+const P = 0.05; // Mutation probability.
+const A2ZS = ["A".."Z"].walk().append(" ").concat();
+fcn fitness(s){ Utils.zipWith('!=,target,s).sum(0) } // bigger is worser
+fcn rnd{ A2ZS[(0).random(27)] }
+fcn mutate(s){ s.apply(fcn(c){ if((0.0).random(1) < P) rnd() else c }) }
+
+parent := target.len().pump(String,rnd);  // random string of "A..Z "
+gen:=0; do{  // mutate C copies of parent and pick the fittest
+   parent = (0).pump(C,List,T(Void,parent),mutate)
+	    .reduce(fcn(a,b){ if(fitness(a)<fitness(b)) a else b });
+   println("Gen %2d, dist=%2d: %s".fmt(gen+=1, fitness(parent), parent));
+}while(parent != target);