PROPOSAL: fold keyword

[Joshua Bloch]

Gabriel,

This doesn't seem compelling.

Here's your simple example:

    // sum all numbers in the list
    Integer sum =
    fold(Integer n : list;     // iterating collection element n
         Integer result = 0) { // Where to accumulate the result, and
             the initial value
             result += n;
         };
    }

And here's how it looks today (with no change to the language or libraries):

    Integer sum = 0;
    for (Integer n : list)
        sum += n;


Here's one of your complex examples:

  // returns a new collection with the salaries of the employees not on
vacation
 List<BigDecimal> salaries =
   fold(Employee e : emps;
        List<BigDecimal> newList = new ArrayList<BigDecimal>()) {
     if (!e.onVacation()) {
       newList.add(e.getSalary());
     }
   }

And here's how it looks today:

     List<BigDecimal> salaries = new ArrayList<BigDecimal>();
     for (Employee e : emps)
         if (!e.onVacation())
             salaries.add(e.getSalary());

To my eyes, the current version is clearer as well as shorter.

            Josh