Devoxx - filter, partition and offset

[Jed Wesley-Smith]

On 3 April 2013 22:36, Stephen Colebourne <scolebourne at joda.org> wrote:
> It didn't come up in the Devoxx lab, but I found the filter() method
> confusing when reading code in the talks. It was not obvious to me
> whether it was filtering in or out.
>
> I was then surprised that there was only one method in the API for
> filtering, rather than two - one to remove and one to retain. While
> clearly they are a logical not, in code readbility terms its typically
> a lot clearer.
>
> Perhaps keep() and reject()? I'm sure there are other names, but
> filter alone feels very unclear. (I can't remember which it is now).

Haskell:
http://www.haskell.org/ghc/docs/latest/html/libraries/base/Data-List.html#v:filter

Scala:
http://www.scala-lang.org/api/current/index.html#scala.collection.immutable.List

Standard ML:
http://www.standardml.org/Basis/list.html#SIG:LIST.filter:VAL

Erlang:
http://www.erlang.org/doc/man/lists.html#filter-2

Guava:
http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/Iterables.html#filter(java.lang.Iterable,
com.google.common.base.Predicate)

Wikipedia:
http://en.wikipedia.org/wiki/Filter_(higher-order_function)

all define the same behaviour and name of this method.

It is sufficiently commonplace that to define it differently would be
arbitrary and random.

cheers,
jed.