Welcome to darlang’s documentation!¶

Basics¶

This document is very incomplete, perhaps some meaning can be derived from it.

Declarations¶

func(arg_1, arg_2, ..., arg_n) -> expr

All functions in darlang are implicitly typed. Both the argument types and the return value are derived through unification by the callee and implementation, respectively.

Binding¶

id | expr; ...

Binding is the process of assigning an expression to a new identifier in the current scope. All references to the id on the left hand side of the expression will be substituted with the associated expression.

Conditionals¶

{
  case_1 : expr_1;
  case_2 : expr_2;
  ...
  case_n : expr_n;
       * : expr_wildcard;
}

Darlang uses a singular guard-like construct to provide control flow.

Cases are evaluated from top to bottom- the first true case expression will cause the associated expression to be returned.

All branching constructs must have a “wildcard” case, to be executed when no cases are satisfied.

Example¶

Let’s get started with a program that computes the classic Euclidean algorithm.

euclid(a, b) ->
  {
    is(b, 0) : a;
           * : euclid(b, mod(a, b))
  }

main() -> euclid(15, 10)

Types¶

Primitives¶

Product types¶

Disjoint unions¶

Specialization¶

Specialization is the mechanism through which darlang provides parametric function polymorphism. It can be seen as an analogue to implicitly-generated C++ templates, implementation-wise.

Specialization at work¶

Suppose the existence of an under-constrained function tuplify;

tuplify(a) -> (a, a)

Such a function can be observed to impose no constraints on the type of the argument a. Since the set of potential types for tuplify is infinite, the darlang compiler skips code generation for it in the absence of invocations.

Consider, however, if we had the following invocations:

main() ->
  ds | tuplify("hello");
  is | tuplify(5);
  0

Two specializations of tuplify are generated by the compiler- one with signature string -> (string, string), and one with signature i64 -> (i64, i64). This reduces the need for runtime typing logic, reducing instruction count at the expense of code size.

Note

Specializations of a function are populated by the darlang compiler by traversing the call graph starting from top-level exports, which possess known types, and enumerating all required implementations.

IR is generated for each possible specialization of a function, each of which possess a unique symbol name derived from the function’s name and its solved argument types.

Quirks¶

All values of a recursive type are enforced to be heap allocated.