poly

A nim library for variant-based overloading

example

poly:
  proc display*(a: A{kind: A1}, b: string) {.async.} =
    echo b, " ", a.a1


  proc display*(a: A{kind: A2}, b: string) {.async.} =
    echo b, " ", a.a2

# equivalent to

# proc display*(a: A; b: string) {.async.} =
#   case a.kind
#   of A1:
#     echo b, " ", a.a1
#   of A2:
#     echo b, " ", a.a2

(full in example.nim)

Poly checks that args, return and pragmas in overloads are the same. If you just pass a: A, you can generate else

If I have a lot of logic for each variant, of gets messy and I have to refactor it in functions. Then I need to manually dispatch to those functions in case and to do assert in them in order to have type safety: with poly I just need to write the kind in signatures

name

I can't think of another name: poly,morphism

future

probably one can add support for full pattern matching, e.g.

poly:
  proc display*(a: A{e: 4, h > 2}) =
    echo a.e

generating if

However maybe patty is a better place for that