Plum

Plum is a programming language for writing functional, fast, reusable code.

Functional: Functions can't have side effects. Data is immutable and acyclic. Code is eagerly evaluated.

Fast: Types are known at compile time. Values have an efficient memory layout.

Reusable: You can write generic code. You can inspect types at compile time.

Intro

Type names are always uppercase. Type variables are lowercase. Use & to create structs and | to create enums.

Json =
  | Int Int
    Map (Map String Json)
    Bool Bool

List t = & buffer: (Buffer t) len: Int

Function names are always lowercase or symbols. The signatures of functions have type annotations that allow you to figure out the return type without looking at the body.

+ a: Int b: Int = builtins.add a b
+ a: String b: String = builtins.concat a b

get list: (List t) index: Int -> t = ...
get map: (Map k v) key: k -> v = ...

parse json: Json target: Type -> target =
  type_info target
  % Int:
      json
      % Int int: int
        else: crash "Expected int, found other stuff."
    Struct fields:
      json
      % Map map:
          ...
        else: crash ...