SnowyOwl

Indeed, the type system when explained in detail is not that simple. Nevertheless, we believe that it can be used without detailed knowledge.

In our experience, programmers can pick up the system fast (e.g. after a 2 hour discussion).

Similarly, programmers can easily write programs which type-check, even if they do not have a deep understanding of the type system (e.g. they need not memorise the table you mentioned). Type-checking is enough - given the guarantees by the type system, (data-race freedom and atomicity).

The use of defaults reduces the annotation burden - typically to only 10%-20% of locations which allow them.

In Akka, message arguments have to be immutable objects - similarly for Erlang; Pony can pass isolated references which can be mutated and passed on, while still being data-race free. Scala is based on Java, and thus it is not data-race free - unless the program has been crafted very carefully.

Indeed, Pony can automatically detect actors with empty stacks and message queues, also when these are part of a cycle.

We will have more benchmarks soon. Pony is between 2 and 3 times faster than Erlang on these benchmarks.

Do you mean whether Pony requires/allows braces to delimit functions, or class definitions? If so, the answer is no, as they are superfluous.

Actor based; type safe; data-race free; copy-less message passing; easy to write fast programs; non-null types; algebraic data types; ...

Is there a specific language you would like to compare with?