RosettaCodeData/Task/Evolutionary-algorithm/Elena/evolutionary-algorithm.elena

import system'routines;
import extensions;
import extensions'text;

const string Target = "METHINKS IT IS LIKE A WEASEL";
const string AllowedCharacters = " ABCDEFGHIJKLMNOPQRSTUVWXYZ";

const int C = 100;
const real P = 0.05r;

rnd = randomGenerator;

randomChar
    = AllowedCharacters[rnd.nextInt(AllowedCharacters.Length)];

extension evoHelper
{
    randomString()
        = 0.repeatTill(self).selectBy:(x => randomChar).summarize(new StringWriter());

    fitnessOf(s)
        = self.zipBy(s, (a,b => a==b ? 1 : 0)).summarize(new Integer()).toInt();

    mutate(p)
        = self.selectBy:(ch => rnd.nextReal() <= p ? randomChar : ch).summarize(new StringWriter());
}

class EvoAlgorithm : Enumerator
{
    object theTarget;
    object theCurrent;
    object theVariantCount;

    constructor new:of(s,count)
    {
        theTarget := s;
        theVariantCount := count.toInt();
    }

    get() = theCurrent;

    bool next()
    {
        if (nil == theCurrent)
            { theCurrent := theTarget.Length.randomString(); ^ true };

        if (theTarget == theCurrent)
            { ^ false };

        auto variants := Array.allocate(theVariantCount).populate:(x => theCurrent.mutate:P );

        theCurrent := variants.sort:(a,b => a.fitnessOf:Target > b.fitnessOf:Target ).at:0;

        ^ true
    }

    reset()
    {
        theCurrent := nil
    }

    enumerable() => theTarget;
}

public program()
{
    var attempt := new Integer();
    EvoAlgorithm.new:Target &of:C.forEach:(current)
    {
        console
            .printPaddingLeft(10,"#",attempt.append(1))
            .printLine(" ",current," fitness: ",current.fitnessOf(Target))
    };

    console.readChar()
}