PLT Scheme v4.2.4
posted by Eli Barzilay
PLT Scheme version 4.2.4 is now available from http://plt-scheme.org/
- The
scheme/flonum
andscheme/fixnum
libraries provide flonum- and fixnum-specific operations. In the case of flonum-specific operations, the JIT compiler can recognize combinations of operations (including local bindings) and improve performance by “unboxing” intermediate results. - The
scheme/unsafe/ops
library provides arithmetic and other operations that are implemented without dynamic checks. Avoiding checks can sometimes improve performance, but at the expense of safety. 2htdp/universe
: We have severed the connection between universe and an image library and made a few other, minor changes. Most programs will now have to change to require thehtdp/image
library explicitly. For the full details, see the new Porting World Programs section of the documentation.- The
2htdp/image
library continues to grow. In this release, it is supported by2htdp/universe
, equality changed to be based on how the images are drawn, cropping and curves were added, and support for more kinds of pens were added. htdp/world
: The old world teachpack remains deprecated. HtDP/2e exclusively uses the new 2htdp/universe library. For backwards compatibility, the world teachpack will remain in the distribution until the coming summer.- The
scheme/class
library now providesthis%
, which refers to the class of the current object (i.e.this
). scheme/generator
has convenient functions for infinite generators, and for converting a generator to a sequence for iteration.- PLT Scheme’s add-on directory can be customized by the
$PLTADDONDIR
environment variable or--addon
/-A
command-line flags. This controls where downloaded Planet packages and their compiled Scribble documentation are installed. - Additional extensions include: saving
errno
in foreign calls, much improvedsort
speed, normalized results fromprocedure-arity
, and more.