While preparing the Cloje 0.2 release last week, I came across something I had written, part of the goals for Cloje:
Importing all of Cloje will allow you to write code in a language very similar to Clojure. Or if you prefer, you will be able to pick and choose which pieces of Cloje to import, so that you are still mostly writing code in Scheme/Lisp, but with some added features from Clojure.
I had written that over a month ago, long before I had explored host interop issues. Reading it again during the release preparations made me wonder if I had neglected this use case when considering the host interop API design.
My consideration of host interop was from the angle of someone who was writing in Cloje, and wanted to interact with certain host language features or libraries. I hadn’t really considered someone who was writing in the host language, and wanted to integrate certain Cloje features or libraries. It made me wonder whether it was accurate to say that users would be able to “mostly write code in Scheme/Lisp”, considering that much of Cloje will probably depend on a bunch of new types.
This got me thinking on a more fundamental level about Cloje’s stance regarding host types. Should it be possible (and acceptable/idiomatic) for Cloje users to decide to write Cloje programs that primarily (or exclusively) use host types? Or are Cloje users expected to primarily use Cloje types, and only use host types for host interop?
Note: When I talk about “Cloje types” and “host types” in this post, I am mostly thinking of lists, vectors, hash maps/tables, and strings. Those are the types where Cloje and the host language would have “colliding” types (analogous types with different implementations), and thus the source of possible trouble. Certain other types (such as symbols, numbers, and functions) are the same type in Cloje as on the host, so no conversion (implicit or explicit) would be needed.
To help me organize my thoughts and guide my decision, I have sketched out a few scenarios for different stances Cloje might take regarding host types, and explored some of the implications of each scenario. Continue reading Cloje types vs host types, revisited