Racket v5.0.1

Racket version 5.0.1 is now available from

  http://racket-lang.org/

• Datalog is a lightweight deductive database system with Racket integration. It is now available in the datalog collection and with #lang datalog.
• Racklog provides Prolog-style logic programming in Racket, adapted from Dorai Sitaram's Schelog package. It is available in the racklog collection and now as #lang racklog.
• By default make install and raco setup compile collections in parallel on all available processors. (Use raco setup -j 1 to disable, if necessary.)
• Changes (as part of 5.0) in the racket language compared to the scheme language: constructor-style printing, a struct alternative to define-struct that fits more naturally with match and constructor-style printing, bytecode-dependency management via SHA-1 hashes instead of just timestamps (where the openssl/sha1 library provides the SHA-1 hash function), a reorganization of scheme/foreign into ffi/unsafe and associated libraries, and new printing functions eprintf and displayln. Also, a generator from racket/generator is required to have the form (generator () body ...), which supports a planned extension to let a generator accept arguments.
• Changes to the racket language (since 5.0): internal-definition positions allow mixing expressions with definitions, full continuations can escape past a continuation barrier, custodians can attempt to terminate subprocesses and subprocess groups (see current-subprocess-custodian-mode, subprocess-group-enabled), the JIT supports additional unboxing flonum operations and unsafe variants, ffi/unsafe provides an asychronous-call mechanism to deal with foreign threads, a new "." modifier for format string directives (e.g., "~.s" and "~.a") limits the respective output to (error-print-width) characters.
• The core type system of Typed Racket has been substantially revised. In particular, Typed Racket can now follow significantly more sophisticated reasoning about the relationships between predicates. Additionally, Typed Racket now allows variable arity types in more places, allowing programmers to specify variable-arity lists.
• We are working on an optimizing version of Typed Racket that takes advantage of type information for certain classes of programs. This project is a work in progress. For those interested, see the documentation for #:optimized.
• The web-server/formlets library adds a formlet* form that allows dynamic formlet construction, as opposed to formlet which requires syntactic Xexprs and static formlets. Several new library formlets are added.
• The syntax/parse library has new support for matching literals at different phases using the #:phase argument for literals and literal sets.
• RackUnit now includes a GUI test runner as rackunit/gui.
• The 2htdp/image library now includes flip-vertical and flip-horizontal operations that mirror images (vertically and horizontally).