RELEASE-0.2.md

0.2.0 Changes

Many thanks to the contributors who helped with this release.

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

New Features

• RankNTypes

  This experimental feature allows polymorphic types (introduced with forall) to appear on the left of a function arrow, or as the type of a record field, etc. For example:

    rank2 :: (forall a. a -> a) -> Number
    rank2 = \f -> if f true then f 1 else f 2

• Modules

• Polymorphic Object Update

  Records now support member update in which the type of the field changes during the update. For example:

    data Wrap a = Wrap a
    
    update = \o -> o { prop = Wrap o.prop }

Enhancements

• Naked expressions as statements

  Naked expressions of type {} can now be used as statements.

• Split code generation into AST -> JS and JS -> String

  JavaScript generation is now split into the generation of a JavaScript AST, and the pretty-printing of that AST. This enables some optimizations, and a better JavaScript pretty-printer.

• Syntactic sugar for introducing curried functions

  Single-argument functions and multiple-argument functions can now be introduced in the same way:

    test = \a (b, c) d -> a + b + c + d

• JavaScript optimizations

  Some basic dead-variable elimination, inlining and eta-conversion are now performed on the generated JavaScript.

• Generate formatted Javascript

  The generated JavaScript is now formatted to be more readable. In particular, newlines get generated, and the correct indentation is used.

• More valid infix operators

  The colon and period characters are now valid in infix operator names.

Syntax Changes

• Avoid 'do' keyword for blocks

  do will be used later for Haskell-like monad comprehensions, so its previous use in introducing blocks of statements is now invalid. The do keyword is still reserved.

• Member foreign import syntax

  A small syntactic addition to the FFI, to support a common use case.

• Make FFI syntax match Haskell

  Use foreign import instead of extern.

• Make record declaration syntax match Haskell

• Simplify array binders

  There are now two types of array binders: cons binders x : xs -> ... and array binders [x, y, z] -> ... instead of the previously confusing [x:xs].

• Array indexing syntax is ambiguous

  Array elements are now accessed using the !! operator: arr !! 0 etc.

Bug Fixes

• Allow guards access to current scope

Libraries

• Prelude

  There is now a basic prelude in the libraries/prelude folder.