Updated State of the Lambda

[Yuval Shavit]

I could learn to use any pair of words -- map/reduce, transform/combine, ☃/
foobaz. I slightly prefer map/reduce because it's what seems to be the
standard in languages that already have this functionality.

On Mon, Dec 12, 2011 at 6:43 PM, Dan Smith <daniel.smith at oracle.com> wrote:

> On Dec 12, 2011, at 3:21 AM, Stephen Colebourne wrote:
>
> > int sum = list.map(e -> e.size()).reduce(0, (a, b) -> a+b);
> >
> > I continue to find map/reduce examples for summing a list to be
> > troublesome. I remain concerned that the mental shift involved here is
> > being underestimated, particularly in the context of Java.
> > Specifically, steps that are currently performed as one, are now
> > having to be broken down into multiple parts - map then reduce. Note
> > that I do not think that individual filtering or transformation of
> > lists/maps will prove troublesome, my concern is primarily around
> > multi-step operations and reduce.
>
> Well, you can always perform the steps as one if you want:
>
> int sum = list.reduce(0, (n, e) -> n+e.size());
>
> Should we be criticizing this alternative as a Bad Thing?  I'm not sure
> there's a clear reason to do so.  I think the use of chaining in these toy
> examples is inspired by much bigger problems where there's a clear benefit
> to separating concerns.  (And in this particular case, the use of chaining
> evolved from a time when we were using a 'max' method.)
>
> > I continue to be concerned about the verbs being used and their
> > readability. Clearly these terms are used elsewhere, but I continue to
> > be of the opinion that "map" is the wrong verb for Java, because of
> > Java.util.Map. My preference currently remains as
> > "transform/Transformer". Similarly, I think "combine" may be a better
> > verb than "reduce". With altered verbs, I think the mental shift
> > required is lessened:
> >
> > int sum = list.transform(e -> e.size()).combine(0, (a, b) -> a+b);
>
> +1 on 'combine'.  'map' doesn't bother me (I'd even like to see Map
> implement Mapper :-) ), but 'combine' seems to clearly convey the behavior
> more explicitly than 'reduce'.
>
> —Dan
>
>