• via Digitalmars-d-bugs (30/30) Jul 03 2014 https://issues.dlang.org/show_bug.cgi?id=13029

via Digitalmars-d-bugs <digitalmars-d-bugs puremagic.com> writes:

https://issues.dlang.org/show_bug.cgi?id=13029

          Issue ID: 13029
           Summary: cumulate for std.algorithm
           Product: D
           Version: D2
          Hardware: x86_64
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: Phobos
          Assignee: nobody puremagic.com
          Reporter: jens.k.mueller gmx.de

cumulate is an algorithm that I use rarely but still I believe it belongs into
the standard library.
cumulate applies a binary function to a range in a cumulative manner. Matlab
has cumsum and cumprod (see
http://www.mathworks.de/de/help/matlab/ref/cumsum.html and
http://www.mathworks.de/de/help/matlab/ref/cumprod.html).

Some unittests to define its behavior.

unittest
{
   assert([].cumulate!((a,b) => a + b).equal([]));
   assert([1].cumulate!((a,b) => a + b).equal([1]));
   assert([1,2,3].cumulate!((a,b) => a + b).equal([1,3,6]));
}

It may very well be the case that one can express this functionality using
other functions from std.algorithm. If there is an easy approach, I may follow
that way. I couldn't fine one.

--