Category talk:Wren-trait

Source code

<lang ecmascript>/* Module "trait.wren" */

/*

   Comparable is an abstract class which enables child classes to automatically
   inherit the comparison operators by just overriding the 'compare' method.

• /

class Comparable {

   compare(other) {
       // This should be overridden in child classes to return -1, 0 or +1
       // depending on whether this < other, this == other or this > other.
   }

   < (other) { compare(other) <  0 }
   > (other) { compare(other) >  0 }    
   <=(other) { compare(other) <= 0 }
   >=(other) { compare(other) >= 0 }
   ==(other) { compare(other) == 0 }
   !=(other) { compare(other) != 0 }

}

/* Cloneable is an abstract class which enables child classes to automatically be

  recognized as 'cloneable' by overriding the 'clone' method.

• /

class Cloneable {

   clone() { /* to be overridden by child class */ }

}

/* CloneableSeq is an abstract class which enables child classes to automatically be

  recognized as both Sequences and 'cloneable' by overriding the 'clone' method.

• /

class CloneableSeq is Sequence {

   clone() { /* to be overridden by child class */ }

}

/* Stepped wraps a Sequence so it can be iterated by steps other than 1. */ class Stepped is Sequence {

   // Constructs a new stepped sequence.
   construct new(seq, step) {
       if (!(seq is Sequence)) Fiber.abort("First argument must be a sequence.")
       _seq = seq
       _step = (step < 1) ? 1 : step // minimum step of 1
   }

   // Iterator protocol methods.
   iterate(iterator) {
       if (!iterator) {
           return _seq.iterate(iterator)
       } else {
           var count = _step
           while (count > 0 && iterator) {
              iterator = _seq.iterate(iterator)
              count = count - 1
           }
           return iterator
       }
   }

   iteratorValue(iterator) { _seq.iteratorValue(iterator) }

}

/*

   Reversed wraps a Sequence (other than a range) so it can be iterated in reverse
   and by steps other than 1.

• /

class Reversed is Sequence {

   // Constructs a new reversed sequence.
   construct new(seq, step) {
       if (!(seq is Sequence) || seq is Range) {
           Fiber.abort("First argument must be a sequence other than a range.")
       }
       _seq = seq
       _step = (step < 1) ? 1 : step // minimum step of 1
   }

   // Convenience method which calls the constructor with a step of 1.
   static new(seq) { Reversed.new(seq, 1) }

   // Iterator protocol methods.
   iterate(iterator) {
       var it = _seq.iterate(iterator)
       if (it == null || it == 0) {
           it = _seq.count - 1
       } else if (it == false) {
           it = _seq.count - 1 - _step
       } else { 
           it = it - 1 - _step
       }       
       return (it >= 0) ? it : false
   }

   iteratorValue(iterator) { _seq.iteratorValue(iterator) }

}

// Type aliases for classes in case of any name clashes with other modules. var Trait_Comparable = Comparable var Trait_Cloneable = Cloneable var Trait_CloneableSeq = CloneableSeq var Trait_Stepped = Stepped var Trait_Reversed = Reversed</lang>