Bincheng Wu - Journal: 2023

Sunday, December 31, 2023

Dot selection

Koka is a function-oriented language where functions and data form the core of the language (in contrast to objects for example). In particular, the expression s.encode(3) does not select the encode method from the string object, but it is simply syntactic sugar for the function call encode(s,3) where s becomes the first argument. Similarly, c.int converts a character to an integer by calling int(c) (and both expressions are equivalent). The dot notation is intuïtive and quite convenient to chain multiple calls together, as in:
fun showit( s : string )
  s.encode(3).count.println
for example (where the body desugars as println(count(encode(s,3)))). An advantage of the dot notation as syntactic sugar for function calls is that it is easy to extend the ‘primitive’ methods of any data type: just write a new function that takes that type as its first argument. In most object-oriented languages one would need to add that method to the class definition itself which is not always possible if such class came as a library for example.

The Koka Programming Language

Minimal but General

Koka has a small core set of orthogonal, well-studied language features – but each of these is as general and composable as possible, such that we do not need further “special” extensions. Core features include first-class functions, a higher-rank impredicative polymorphic type- and effect system, algebraic data types, and effect handlers.

Koka - A Functional Language with Effect Types and Handlers