cumulate

[Doug Lea]

On 12/21/12 16:31, Brian Goetz wrote:
>
> In Arrays:
>    void parallelPrefix(T[], int offset, int length, BinaryOperator<T>);
>    void parallelPrefix(int[], int offset, int length, IntBinaryOperator);
>    void parallelPrefix(long[], int offset, int length, LongBinaryOperator);
>    void parallelPrefix(double[], int offset, int length, DoubleBinaryOperator);
>

The reason I initially suggested a name other than "parallelPrefix"
is that the term is used with either of two subtly different
variations; one computing (in place) the cumulation up to but not
including each element, and the other including the element.
Given the parameterization, our version can only be the
latter. (Otherwise it would require an identity base and
return total.) So I'm OK with it, but still slightly nervous.

Example:
[1, 2, 3, 4] ->  modify in place to:
   v1   [0, 1, 3,  6] -> return 10
   v2   [1, 3, 6, 10] -> void      (our version.)

Each of the versions is a little handier than the other for
some purposes. But it is easy enough to adapt any usages
of one to use the other.

-Doug