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RELEASE-0.4.md

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0.4.0 Changes

This release focussed mainly on bug fixes and minor enhancements, in order to provide a stable release of the compiler.

This release saw major contributions from a number of new contributors. Thank you very much to everyone who submitted pull requests, issues and suggestions, and also to the users of the #purescript FreeNode channel for their valuable feedback. As always, new contributors are always welcome!

  • The full language guide can be found here.
  • Try out the latest features here.

Breaking Changes

  • Multiple argument functions are no longer available.
  • When used in the browser, PureScript modules are now accessed through window.PS.<ModuleName>. The PS object name can be changed via the --browser-namespace compiler argument.
  • The --run-main argument has been replaced with --main which can now accept a module name in which to find the main function.

New Features

  • Dead code elimination. The new compiler argument --module= can be used to specify one or more modules that should be kept in the generated code along with their dependencies. If no modules are specified, all code is exported.

Enhancements

  • The -> and [] types are now usable in type class instances.
  • The file path is included in syntax error messages.
  • Most reserved Javascript names (return, const, etc) are now usable.
  • Generated code for operators is more user friendly (for example, Prelude[">>="]). Where this transformation cannot be applied, human-readable variable names (e.g. $greater$greater$eq) are generated.
  • The typechecker's function application judgement was greatly simplified, and as a result, more valid things now typecheck.
  • Data constructors with multiple arguments can now be defined.
  • It is no longer necessary to sort modules in order of dependencies manually.
  • Case statements matching data constructors no longer generate unnecessary constructor checks at runtime if there is only a single data constructor.
  • New optimizer rules were added to inline JavaScript's built-in operators.

Bug Fixes

  • Floats parse correctly.
  • Using data constructors in pattern matches now works properly across modules.
  • PureScript modules no longer overwrite global objects with the same name.
  • Show problems with shadowing of names were fixed.
  • Problems with recursive non-function values were fixed.
  • Type synonyms can now expand to types containing more type synonyms.
  • A bug in capture-avoiding type variable substitution which was affecting the Functor (Either e) instance was fixed.
  • Type synonym instances are now disallowed.
  • Precedence rules for some basic operators were corrected.
  • A bug which allowed skolem variables to escape their scope was add (thanks to Brian McKenna).
  • Modules containing mutually recursive type synonyms and data declarations now compile correctly.
  • A number of bugs in the optimizer were addressed.

Libraries

  • The Prelude has been greatly expanded. Definitions for built-in JavaScript operators have been moved into the Prelude.
  • Gary Burgess has released the grunt-purescript library to build PureScript code using Grunt.
  • The purescript-parsing library provides Parsec-like parsing combinators.
  • The purescript-promises library provides Monad and Applicative instances for promises.
  • The purescript-quickcheck library provides a very basic implementation of a QuickCheck-style testing harness.
  • The purescript-json library aims to provide a safe way to consume JSON data.

Documentation

  • Documentation for the Prelude modules is now automatically generated and can be found here.
  • There is now Hackage documentation.
  • Code comments have been improved.