Retiring unstable

Some of you may be familiar with the unstable collection, whose
purpose was to serve as a staging ground for new APIs that hadn't yet
found a more permanent home. With the advent of the package system,
packages can serve that same purpose, which removes the need for a
dedicated unstable collection provided by the main distribution.

For this reason we are moving unstable-* packages out of the main
distribution.

For backwards compatibility, the packages remain available from the
package catalog. Packages that properly list their dependencies (as they
should! it's an error not to!) are unaffected by this change. Packages
that are missing dependencies may need to be adjusted to include the
appropriate unstable dependencies.

The unstable packages contained many useful functions and APIs, and we
merged many of them into established Racket libraries. Others were spun
off as their own packages. The remaining APIs, which we judged too
narrow or too immature, we left in unstable packages, where they are
still available in their original form. In all cases, the original
unstable libraries continue to export the same bindings they always
did, to ensure backwards compatibility.

For completeness, here is a list of the fate of each unstable library
that used to be part of the main distribution.

• unstable/2d

  • Moved to the 2d package.

• unstable/arrow

  • Left in unstable-lib.

• unstable/automata

  • Moved to the automata package.

• unstable/bytes

  • Left in unstable-lib.

• unstable/class-iop

  • Moved to the class-iop package.

• unstable/contract

  • Moved non-empty-string? to racket/string.
  • Moved port-number? and tcp-listen-port? to racket/tcp, the
    latter renamed to listen-port-number?.
  • Moved if/c, failure-result/c, predicate/c and
    rename-contract to racket/contract.
  • Moved treeof to plot/utils.
  • Moved sequence/c to racket/sequence.
  • Left path-piece?, maybe/c, truth/c in unstable-contract-lib.

• unstable/custom-write

  • Moved make-constructor-style-printer to racket/struct.
  • Left prop:auto-custom-write in unstable-lib.

• unstable/debug

  • Left in unstable-debug-lib.

• unstable/define

  • Left in unstable-lib.

• unstable/error

  • Left in unstable-lib.

• unstable/find

  • Left in unstable-lib.

• unstable/flonum

  • Superceded by math/flonum. Left in unstable-flonum-lib.

• unstable/function

  • Merged with racket/function.

• unstable/future

  • Merged with racket/future.

• unstable/gui/notify

  • Moved to framework/notify, with naming changes.

• unstable/gui/pict

  • Moved color/c, light, dark, red, orange, yellow, green,
    blue, purple, black, brown, gray, white, cyan, and
    magenta to pict/color.
  • Moved show, hide, pict-if, pict-cond, and pict-case to
    pict/conditional.
  • Merged scale-to with pict's scale-to-fit.
  • Merged ellipse/border, circle/border, rectangle/border,
    rounded-rectangle/border with pict's ellipse, circle,
    rectangle, and rounded-rectangle, respectively.
  • Merged pin-label-line, pin-arrow-label-line, and
    pin-arrows-label-line with pict's pin-line, pin-arrow-line,
    and pin-arrows-line, respectively.
  • Moved blur, shadow, and shadow-frame to pict/shadow.
  • Moved unstable/gui/pict/align to ppict/align, in the ppict
    package.
  • Left color, pict-match, pict-combine, with-pict-combine,
    fill, strike, shade, blur-bitmap!, arch,
    draw-pict-centered, backdrop, cross-out, and
    make-plt-title-background in unstable-lib.

• unstable/gui/ppict

  • Moved to the ppict package.

• unstable/gui/prefs

  • Moved to framework/preferences, with naming changes.

• unstable/gui/redex

  • Left in unstable-redex.

• unstable/gui/scribble

  • Left in unstable-lib.

• unstable/gui/slideshow

  • Moved with-size, with-scale, big, small, with-font,
    with-style, bold, italic, subscript, superscript, caps,
    and blank-line to slideshow/text.
  • Moved slide/staged, staged, stage, stage-name, at,
    before, after, before/at, after/at to the staged-slide
    package.
  • Left column, columns, column-size, two-columns,
    mini-slide, tabular, reveal, revealing-slide, and
    items-slide in unstable-lib.

• unstable/gui/snip

  • Left in unstable-lib.

• unstable/hash

  • Merged with racket/hash.

• unstable/latent-contract

  • Left in unstable-latent-contract-lib.

• unstable/lazy-require

  • lazy-require has been in racket/lazy-require for some time.
  • Left begin-on-demand in unstable-lib.

• unstable/list

  • Moved check-duplicates, remf, remf*, group-by,
    cartesian-product, list-update, and list-set to racket/list.
  • Moved list-prefix?, take-common-prefix, drop-common-prefix,
    and split-common-prefix to racket/list, with slight API changes
    to harmonize with Racket's list API.
  • Left filter-multiple, extend, map/values, and map2 in
    unstable-list-lib.

• unstable/logging

  • Moved with-intercepted-logging and with-logging-to-port to
    racket/logging.
  • Left start-recording and stop-recording in unstable-lib.

• unstable/macro-testing

  • Moved to syntax/macro-testing.

• unstable/markparam

  • Moved to the markparam package.

• unstable/open-place

  • Moved open-place to racket/place, and renamed it place/context.

• unstable/options

  • Moved to the option-contract package.

• unstable/parameter-group

  • Moved to the parameter-group package.

• unstable/pretty

  • Merged pretty-format/write, pretty-format/display, and
    pretty-format/print with racket/pretty's pretty-format.
  • Left break-lines in unstable-pretty-lib.

• unstable/recontract

  • Merged with racket/contract some time ago.

• unstable/sandbox

  • Merged with scribble/eval.

• unstable/sequence

  • Moved in-syntax and in-slice to racket/sequence.
  • Left in-pairs, in-sequence-forever, and sequence-lift in
    unstable-lib.

• unstable/socket

  • Moved to the unix-socket package.

• unstable/string

  • Left in unstable-lib.

• unstable/struct

  • Moved struct->list to racket/struct.
  • Left make in unstable-lib.

• unstable/syntax

  • Moved make-variable-like-transformer to syntax/transformer.
  • Moved syntax-source-directory and syntax-source-file-name to
    syntax/location.
  • Left explode-module-path-index, phase-of-enclosing-module,
    format-unique-id, syntax-length, and syntax-within? in
    unstable/syntax.

• unstable/temp-c

  • Moved to the temp-c package.

• unstable/time

  • Left in unstable-lib.

• unstable/wrapc

  • Moved to syntax/contract.