Metaprogramming approaches to exposing "last"-ness within a traditional for loop. Pretty useless, but a good launching point for exploring metaprogramming. TODO: dynamically applied traits, mixins?, ExpandoMetaClass to override iterator() method? See http://stackoverflow.com/questions/25852346/identify-last-element-of-an-array-in-groovy-for-stat…

ForLoopLastness.groovy

import groovy.transform.TupleConstructor

// approach 1. Custom subtype coercion    
@TupleConstructor
class LastAwareIterator<T> implements Iterator<T> {
    Iterator itr
    boolean hasNext() {
        itr.hasNext()
    }
  
    void remove() {
        itr.remove()
    }
    
    T next() {
        T obj = itr.next()
        boolean last = !itr.hasNext()
        obj.metaClass.isLast << { -> last }
        obj
    }
}
    
class LastAwareList<T> extends ArrayList<T> {
    Iterator<T> iterator() {
        new LastAwareIterator(super.iterator())
    }
}

def list = [1,2,3,4,2] as LastAwareList
for (ai in list) {
    if (ai.last) {
        print 'and '
    }
    print "$ai "
} // prints: 1 2 3 4 and 2

// approach 2: dynamic traits
// ...