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30 changes: 23 additions & 7 deletions README.md
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Expand Up @@ -3,13 +3,29 @@ dotty

[![Build Status](https://travis-ci.org/lampepfl/dotty.png?branch=master)](https://travis-ci.org/lampepfl/dotty)

Dotty is a platform to try out new language concepts and compiler technologies for Scala. The focus is mainly on simplification. We remove extraneous syntax (e.g. no XML literals), and try to boil down Scala's types into a smaller set of more fundamental constructors. The theory behind these constructors is researched in [DOT](http://www.cs.uwm.edu/~boyland/fool2012/papers/fool2012_submission_3.pdf), a calculus for dependent object types.

The dotty compiler is largely a new design. It takes a more functional approach than current scalac, paired with aggressive caching to achieve good performance. At present, only the frontend (parser and type-checker) exists; the transformation and code generation phases remain to be written. Some parts, in particular those that have to do with configuration and input/output are derived from the Scala compiler.

We expect that, over time, some of the new technologies explored in this project will find their way into future versions of Scala. At present it is too early to say which ones and when.

If you want to try it out, to get started have a look at https://github.com/lampepfl/dotty/wiki/Getting-Started.
Dotty is a platform to try out new language concepts and compiler
technologies for Scala. The focus is mainly on simplification. We
remove extraneous syntax (e.g. no XML literals), and try to boil down
Scala's types into a smaller set of more fundamental constructors. The
theory behind these constructors is researched in
[DOT](http://www.cs.uwm.edu/~boyland/fool2012/papers/fool2012_submission_3.pdf),
a calculus for dependent object types.

The dotty compiler is largely a new design. It takes a more functional
approach than current scalac, paired with aggressive caching to
achieve good performance. Some parts, in particular those that have to
do with configuration and input/output are ported from the Scala
compiler. The compiler is fully functional, in particular it can
compile itself. But there's more work needed (and planned) on
polishing rough edges, improving diagnostics, improving compilation
speed, and embedding in other tools.

We expect that, over time, some of the new technologies explored in
this project will find their way into future versions of Scala. At
present it is too early to say which ones and when.

If you want to try it out, to get started have a look at
https://github.com/lampepfl/dotty/wiki/Getting-Started.

Developers mailing list is https://groups.google.com/forum/#!forum/dotty-internals.

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63 changes: 63 additions & 0 deletions docs/2015-10-23-dotty-compiler-bootstraps.md
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---
layout: blog
post-type: blog
by: Martin Odersky and Dmitry Petrashko
title: We Got LiftOff! The Dotty Compiler for Scala Bootstraps.
---

## We Got Liftoff!

The [Dotty project](https://github.com/lampepfl/dotty)
is a platform to develop new technology for Scala
tooling and to try out concepts of future Scala language versions.
Its compiler is a new design intended to reflect the
lessons we learned from work with the Scala compiler. A clean redesign
today will let us iterate faster with new ideas in the future.

Today we reached an important milestone: The Dotty compiler can
compile itself, and the compiled compiler can act as a drop-in for the
original one. This is what one calls a *bootstrap*.

## Why is this important?

The main reason is that this gives us a some validation of the
*trustworthiness* of the compiler itself. Compilers are complex beasts,
and many things can go wrong. By far the worst things that can go
wrong are bugs where incorrect code is produced. It's not fun debugging code that looks perfectly
fine, yet gets translated to something subtly wrong by the compiler.

Having the compiler compile itself is a good test to demonstrate that
the generated code has reached a certain level of quality. Not only is
a compiler a large program (44k lines in the case of dotty), it is
also one that exercises a large part of the language in quite
intricate ways. Moreover, bugs in the code of a compiler don't tend to
go unnoticed, precisely because every part of a compiler feeds into
other parts and all together are necessary to produce a correct
translation.

## Are We Done Yet?

Far from it! The compiler is still very rough. A lot more work is
needed to

- make it more robust, in particular when analyzing incorrect programs,
- improve error messages and warnings,
- improve the efficiency of some of the generated code,
- embed it in external tools such as sbt, REPL, IDEs,
- remove restrictions on what Scala code can be compiled,
- help in migrating Scala code that will have to be changed.

## What Are the Next Steps?

Over the coming weeks and months, we plan to work on the following topics:

- Make snapshot releases.
- Get the Scala standard library to compile.
- Work on SBT integration of the compiler.
- Work on IDE support.
- Investigate the best way to obtaining a REPL.
- Work on the build infrastructure.

If you want to get your hands dirty with any of this, now is a good moment to get involved!
To get started: <https://github.com/lampepfl/dotty>.