//---------------------------------------------------------------------// name: polymorph.ck// desc: example showing polymorphism using a base class and two//       subclasses that each implement their own play() function;//       a generic array of base class references is initialized//       with the more specific subclass instances; this allows//       for .play() to be called during the loop, the behavior of//       which can take on different forms depending on the specific//       type of underlying subclass.////       philosophically, polymorphism in programming amounts to//       a structured way to "break" the established contract between//       a type system and the programmer, allowing objects of//       apparently the same type to exhibit different behaviors.//// author: Ge Wang (https://ccrma.stanford.edu/~ge/)// date: Winter 2023//---------------------------------------------------------------------// generic base classclass Motif{    // default method to be potentially overridden in subclasses    fun void play()    {        <<< "base class Motif.play()", "" >>>;    }} // subclass that inherits from Motif// can think of MoA as a more specific kind of Motifclass MoA extends Motif{    // define play behavior for MoA by overriding play()    fun void play()    {        <<< "do Motif A", "" >>>;    }} // subclass that inherits from Motif// can think of MoB as a more specific kind of Motifclass MoB extends Motif{    // define play behavior for MoB by overriding play()    fun void play()    {        <<< "do Motif B", "" >>>;    }} // instantiate array of base class Motif references// each element is a specific kind of Motif[new MoA, new MoB, new MoB, new MoA] @=> Motif @ motifs[]; // array index variable0 => int which; // loopwhile( true ){    // will automatically call the right play() depending on    // the underlying type (MoA vs. MoB) as instantiated above    spork ~ motifs[which].play();        // advance time    300::ms => now;     // cycle which / print divider every cycel    which++; if( which >= motifs.size() )    { 0 => which; cherr <= "--" <= IO.newline(); }    }