Ursa to-do

Version 0.3

Map interface to internet.
Classes: properties, names for List and Map
Structured concurrency: allow the declaration of new scopes, and to run a task in a new scope.
A generator in a comprehension gives a lazy list/map.

To optimize symbol references, evaluate as much as we can at compile time. Any expression with no free variables can be fully evaluated.
Study vau and first-class environments (objects)
Make code readonly. Start with FreeVars. See https://github.com/immutable-js/immutable-js/

Comprehensions: loop [elem, …] and loop {k = v; …}.
100% test coverage.
Tail recursion elimination
self
Streams, and use as interface to files.
Code formatting: have blank lines between top-level multiline lets, and after the last use in a series of uses.
Structs: single-inheritance, data only.
Unions = enums. (Only way to do union types.)
Interfaces: methods only, can be intersected.

Inter-working with C. Initial quick-and-dirty version: allow arbitrary C APIs to be declared (especially for POSIX; later add GLib introspection), and allow C bindings to be generated for Ark values that have C types, and any base Ark type.
Type checking
Extra for sugar where when an object obj is given as the iterator, obj.iter() is automatically used.
Structs
Enums
Traits (use for built-in operators)
Tuples
Variadic functions?
Slices (implement on lists and strings)
Match statement
String interpolation
Long Unicode escapes
Namespaces
Macros: use for syntactic sugar to get e.g. fn a () { }, and for +=
Module system. Mimic Rust: https://doc.rust-lang.org/rust-by-example/mod/split.html