ErlT - experimental Erlang dialect

This repository contains an early prototype of ErlT, an experimental Erlang dialect with first-class support for static typing.

ErlT targets existing Erlang users and codebases. It builds on Erlang to provide greater support for working with large Erlang codebases. It does this by introducing static types in a way which opens the door to greater IDE integration, safer refactorings, and faster, more specific feedback from the compiler.

The main goal of ErlT is enriching Erlang with static typing capabilities. This involves:

• Providing a feasible path for gradually adopting ErlT with static typing for existing teams and codebases.
• Designing and integrating static typing capabilities of ErlT in a coherent and ergonomic way. It should be a language that users want to use.

See more details in ErlT Vision.

ErlT overview

By default, ErlT is checked (i.e. statically typed), but it also allows some functions or modules to be unchecked (i.e. dynamically typed), both to aid migration and to allow code to be written for which we don't yet have a good typing model. ErlT requires adding specs to unchecked code in order for it to be accessible and typeable from checked code.

Scope of the current prototype includes:

• first-class optional static typing model, based on Hindley-Milner
• new first-class data types
  • enums, aka discriminated union types
  • structs, aka first-class nominal records
  • shapes, aka ad-hoc structured records
• interoperability between statically typed (checked) and dynamically typed (unchecked) of the language within a single module
• improved variable scoping model: (almost) lexical scoping and more explicit rules for variable shadowing
• minimal integrations with rebar3

See more details in ErlT Language Overview.

Examples of things that didn't make it into this prototype:

• typing of concurrency primitives
• namespaces and namespace management
• stdlib and library wrapping mechanisms
• IDE/editor integration
• language capabilities to aid the adoption of static typing
• tooling for migrating from Erlang to ErlT

Getting started with ErlT

Read ErlT Language Overview.

To play with ErlT code, see Examples.

Prerequisites:

• erlang with OTP 23 or higher
• rebar3 version 3.14.1 or higher

E.g. on MacOS:

brew install erlang rebar3

Quick Links

• Docs
• Examples
• Tests

Contributing

This project is read-only and not accepting contributions.

Feel free to clone. It is open-sourced under the Apache 2 license. see LICENSE file for details.

Development

For information on how to navigate ErlT development, see the Development Guide.