Iterator Transformation

Amp provides two common transformation helpers for iterators: map and filter.

Further primitives are very easy to implement using Producer with those two as examples.

map()

map() accepts an Iterator and a callable $onEmit that can transform each value into another value.

filter()

filter() accepts an Iterator and a callable $filter. If $filter($value) returns false the value gets filtered, otherwise the value is retained in the resulting Iterator.