Specification

Semi-formal specification of the syntax and semantics of the Hummingbird language.

Variables

There are two types of variable definitions: var and let. The former declares a mutable variable in the scope. The latter declares an immutable variable in the scope.

Immutability is checked at only the reference level. (It ensures that the variable will always refer to the same thing; however mutating properties of that thing can still occur!) Furthermore, this checking happens only at compile time.

var a: Integer = 1
let b: Integer = 2

var a = 1;
var b = 2;

Functions

Hummingbird provides first-class, anonymous functions.

var a = func (x: String) -> String { }

var a = function (x) { };

Inferred return types

In many cases Hummingbird can infer the return type of a function based off of its arguments and body.

var a = func (x: Integer) { return x }

var a = function (x) {
  return x;
};

Dynamic dispatch

Run-time dynamic dispatching is provided through the multi statement.

multi a (b: Integer, c: Integer) -> Integer
func a (b, c) when (b == 0 || c == 0) { return 1 }
func a (b, c) { return b * c }

function a (b, c) {
  switch (false) {
  case !(b == 0 || c == 0):
    return a_1(b, c);
  default:
    return a_2(b, c);
  }
  function a_1 (b, c) {
    return 1;
  }
  function a_2 (b, c) {
    return b * c;
  }
}

Control flow

The expected suite of control flow statements, such as if, for, and while, are provided.

While

var a: Integer = 1
while a < 10 {
  a = a + 1
}
# a will equal 10 here

var a = 1;
while (a < 10) {
  a = a + 1;
}