reduce() with a mutable initial value

[tommack]

In this example (https://github.com/ReactiveX/RxJava/wiki/Mathematical-and-Aggregate-Operators#reduce)

getComingSoonSequence()
    .reduce([], { theList, video ->
                  theList.add("'" + video.getTitle() + "' (" + video.getOpen() + ")");
                  return(theList);
    }).subscribe({ println("Coming Soon: " + it) });

Passing a list into the reduce method seems like it would only be valid if you could guarantee that the Observable would only be subscribed to once. Why isn't there a reduce method that takes a Supplier as its first argument?

[benjchristensen]

That is an excellent question and a major oversight. Same issue with scan.

[benjchristensen]

Added overloads for scan and reduce that take a factory.

[benjchristensen]

We had to revert these changes due to issues shown in #1883. It was done in #1884.

You can instead use collect for the mutable reduce use case which now uses a factory for the initial value.

We'll have to evaluate whether scan needs a new signature to support this and if so add it later in 1.1 with a new name such as scanTo since we can't overload the method due to generics, type erasure and lambdas colliding.