Question about Iterable.reduce signature

[François Sarradin]

Hi all,

I'm looking for an answer to a question about the method reduce. But, I
still haven't found it in archives of the mailing list. So here is my
question:

The current signature of Iterable<T>.reduce is:

    T reduce(T base, BinaryOperator<T> reducer)

I would like to know why the signature doesn't look like this one?

    <U> U reduce (U base, BiOp<T, U> reducer)

where BiOp<T, U> is supposed to represent a function of two arguments of
respective types T and U, that returns a value of type U.

I really think that this other signature can lead to more readable
code. Below is an example with, say, a set of products that you want to buy
in whatever store you want. And you want to know the total.

With the current version of reduce:

    double total = products.map(p -> p.getPrice()).reduce(0.0, (price,
subTotal) -> price + subTotal);

With the other version of reduce in this mail:

    double total = products.reduce(0.0, (p, subTotal) -> p.getPrice() +
subTotal);

I know that there is a method named mapReduce. But I'm still uncomfortable
with it:

    double total = products.mapReduce(p -> p.getPrice(), 0.0, (price,
subTotal) -> price + subTotal);


Regards,

Francois