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Release Notes

The last full release of MIT Scheme was version 7.3.1 in 1994. The first section summarizes the changes that have occurred since version 7.3.1. Following that are changes from previous versions.

Changes from Release 7.3 to 7.4

This highlights some of the more important changes to Scheme since the 7.3.1 release. For complete details, see the `RCS.log' files in the source code.

Changes to Scheme:

• MIT Scheme is now supported under OS/2.
• Illegally-placed internal definitions now signal an error.
• Stream operations from the upcoming new edition of SICP are implemented.
• The load-option procedure is now extensible, allowing users to add their own options to the database.
• Daylight-savings-time information is now included in the decoded time data structure.

Changes to Edwin:

• Cut and paste between Edwin and the system's clipboard (in X11, the "selection" mechanism) is now supported. This support is directly integrated into the kill and yank commands: killing some text (e.g. C-w, C-k, C-M-k) stores that text into the clipboard; yanking text (e.g. C-y, M-y) inserts text from the clipboard. This support is transparent in that it has no effect on Edwin except when some other program puts text into the clipboard.
• Old RCS support has been replaced with VC ("Version Control") as in Emacs 19. VC is significantly easier to use. At present, VC supports only RCS.
• New command: M-x step-expression; steps through the evaluation of a Scheme expression.
• New command: M-x grep, as in Emacs.
• RMAIL and Unix mail files are now stored in Unix text format, regardless of the underlying operating system. This allows these files to be more easily transferred between operating systems.
• The editor variable evaluate-in-inferior-repl now defaults to #t.
• Customizable imaging of characters is now supported. The per-buffer variable char-image-strings holds a vector of 256 strings that determine how characters are displayed. Using an approriate vector allows the use of fonts with extra characters, "hex" displays, compound characters for displaying ISO Latin text in plain ASCII, and lots of other tricks.
• Dired's commands are now more like those in Emacs 19.
• Dired mode is no longer case-sensitive.
• Dired now supports marking of multiple files. Many commands, such as M, C, and R, now work on the marked files if there are any.
• New command in Dired: + creates a new directory.
• OS/2 and Unix only: Fetching mail from a POP server is now supported, using the `popclient' program as a subprocess. Supports three different `popclient' password schemes: standard, Debian GNU/Linux, and Kerberos V4. Do M-x variable-apropos RET pop RET to see the variables that control the use of the `popclient' program.
• OS/2 and Unix only: Compressed files are now fully supported. Edwin can read, write, and append compressed files. Methods are provided to support the `gzip' and `compress' compression programs, using the suffixes `.gz' and `.Z', respectively. If Edwin is attempting to open a file that doesn't exist, but it sees what appears to be a compressed version of that file, it opens the compressed file instead.
• OS/2 and Unix only: In Dired, s now toggles between alphabetic sorting and time sorting.

Changes Specific to Windows:

• Long filenames are now supported.
• The network `\\host\directory' notation is now supported.
• Scheme no longer supports the ^Z end-of-file convention for files. A ^Z appearing in a file is treated as an ordinary character, and output files do not have ^Z placed at their end.
• The runtime system now has better heuristics for determining the user name and home directory.
• The catatonia timeout has been extended to 120 seconds -- much more reasonable on slow machines.
• Window text color now defaults to the system default rather than to black.
• The default window font family and size is now selectable by the environment variable `MITSCHEME_FONT'.
• process-time-clock now returns the process time, rather than the real time, under NT or any variant of Win32 that supports GetProcessTimes.
• A bug has been fixed in the directory reader in which the OS handle was never closed. This was manifested under Windows 3.1 as Edwin being unable to do filename completion or file saving after 32 handles were opened but never closed.

Changes Specific to Edwin under Windows:

• File systems with either long or short file names are now supported. Edwin modifies its behavior depending on the file-system type, for example, using Unix-style `.~n~' backup names with long files.
• Multiple Edwin screens are now supported.
• The handling of windows has been significantly improved; it is now faster and less buggy.
• New Edwin commands include M-x set-font, M-x set-default-font, M-x set-icon, M-x set-foreground-color and M-x set-background-color.

Changes Specific to OS/2 (since the 7.4.1 release):

• The main console window now supports a Copy command. Any text appearing on the window can be copied to the clipboard by marking it with the mouse and invoking the Copy command.
• The main console window now has a menu bar, which provides the following operations: Exit, Copy, Paste, Set font, and About.
• The main console window now has a list of fonts that it tries to use to set the default font, rather than just "4.System VIO". It tries these fonts in order until it finds one. This allows Scheme to be used on systems that don't support the `System VIO' font, as is true of some non-US versions of OS/2.
• Closing the main console window using the window Close command now asks whether you want to kill Scheme or just close the window and leave Scheme running; usually you will want the former. Previously, it did the latter without asking.
• All windows created by Scheme now have icons to give them a distinctive appearance when minimized.
• Compilation of the microcode is supported using IBM Visual Age C++, Watcom C/C++, or EMX/GCC.
• Unix file systems are supported specially, e.g. Linux ext2 or Unix NFS. End-of-line translation is not done for files on such file systems, so that the files are read and written properly.
• The network `\\host\directory' notation is now supported.

Changes Specific to Edwin under OS/2:

• The Close command on the window menu of an Edwin window now acts like C-x C-c if this is the only Edwin window for this process.
• In Dired, S now toggles between showing and hiding system/hidden files; these files are initially hidden.
• Dired has an M command to set the attributes of a file. It prompts for an attribute string such as `+r' or `-h' and makes the corresponding change to the file's attributes.

Changes from Release 7.2 to 7.3

This is an abbreviated list of the changes that have been incorporated in the 7.3 release since the (partial) 7.2 release.

• Support for MS Windows (3.1 and NT).
• Native compiled-code support for DEC Alpha.
• Compiler can now generate C code. This is used to support the Sun SPARC and IBM RS6000 architectures.
• Support for dynamic loading of compiled C code on several operating systems, including HP-UX, OSF/1, SunOS 4, and AIX.
• New data structures: red/black trees and weight-balanced trees.
• Redesign of hash tables makes them much faster and somewhat more flexible.
• Completely new random-number generator. The interface to the random-number generator has been changed to be like that of Common Lisp.
• Record abstraction now uses a special record type to represent records (previously it used vectors). define-structure now creates records by default; these records are identical to those created with the record abstraction.
• call-with-current-continuation is now properly tail-recursive.
• New command-line switch `-no-suspend-file' prevents the generation of `scheme_suspend' files.
• Uncompression of compiled-code debugging information is now memoized to save time when doing many accesses to the same information (a common occurrence).
• Constant space now grows automatically when needed.
• New procedures:

  call-with-values                ;replaces with-values
  current-load-pathname
  error-output-port
  fold-left
  fold-right
  interaction-i/o-port
  notification-output-port
  prompt-for-command-char
  prompt-for-command-expression
  prompt-for-confirmation
  prompt-for-evaluated-expression
  prompt-for-expression
  standard-unparser-method        ;replaces unparser/standard-method
  stream-first
  stream-rest
  symbol<?
  trace-output-port
  

• string-pad-left now truncates from the left instead of the right.
• Argument to make-graphics-device is now a symbol.
• Each REPL now has its own working directory pathname and pathname defaults. set-working-directory-pathname! changes only the value for the current REPL.
• The definitions of the following procedures have been changed to implement more useful behavior:

  string-capitalized?
  string-lower-case?
  string-upper-case?
  substring-capitalized?
  substring-lower-case?
  substring-upper-case?
  

• New Edwin features:

  M-x dabbrev-expand
  M-x describe-syntax
  M-x rcs-ci-locked-files
  M-x rcs-diff
  M-x rcs-list-locked-files
  M-x rcs-log
  M-x recover-file
  M-x show-parameter-list
  M-x sort-lines and other sorting commands
  auto-mode-alist variable (as in Emacs)
  Encryption/decryption of files in Dired
  Undo upgraded to match GNU Emacs 18.57
  Buffers grow/shrink with constant amortized time
  Emacs 19 tags support (multiple tags files, inclusion)
  

• Edwin compression/uncompression commands changed to use gzip instead of compress.
• Edwin now has text-properties mechanism that permits implementation of highlighted and mouse-sensitive regions.

Changes from Release 7.1 to 7.2

This is an abbreviated list of the changes that were incorporated in the (partial) 7.2 release since the 7.1 release.

• Support for MS DOS.
• Native compiled-code support for the Intel i386 and i486 architectures.
• Fixes to MIPS compiled-code support MIPS R3000 with large cache-line sizes.
• Complete redesign of the error system.
• X11 graphics interface redesigned. The new design is smarter about interaction with the window manager (for example, it implements the WM_DELETE_WINDOW protocol) and has some limited support for event handling. Windows are now closed when they are reclaimed by the garbage collector.
• Redesign of I/O ports. New design supports ports that perform both input and output.
• Ports now have better-defined control over blocking mode and terminal mode. Flushing of output buffers is not done automatically, except for the console port.
• New procedures:

  *default-pathname-defaults*
  ->namestring
  ->truename
  close-port
  directory-namestring
  directory-pathname
  directory-pathname-as-file
  enough-namestring
  enough-pathname
  file-access
  file-attributes-direct          ;same as file-attributes
  file-modification-time-direct
  file-modification-time-indirect ;same as file-modification-time
  file-namestring
  file-pathname
  file-readable?
  host-namestring
  i/o-port?
  make-generic-i/o-port
  make-i/o-port
  open-i/o-file
  pathname-simplify
  pathname-wild?
  pathname=?
  port/copy
  port/input-channel
  port/operation
  port/operation-names
  port/output-channel
  port/state
  port?
  record-copy
  record-modifier                 ;replaces record-updater
  set-port/state!
  

• with-input-from-file and with-output-to-file no longer close the port when they are exited abnormally.
• Redefined #!optional and #!rest to be something distinct from symbols.
• Strings now accept "\nnn" octal character escapes, much like those in C.
• Redesign of pathname abstraction. New design is very similar to the Common Lisp pathname abstraction.
  • ->PATHNAME no longer accepts a symbol as an argument. Only strings and pathnames are valid.
  • Procedures eliminated:

    canonicalize-input-filename
    canonicalize-input-pathname
    canonicalize-output-filename
    canonicalize-output-pathname
    canonicalize-overwrite-filename
    canonicalize-overwrite-pathname
    home-directory-pathname
    init-file-truename
    pathname->absolute-pathname
    pathname->input-truename
    pathname->output-truename
    pathname->overwrite-truename
    pathname->string
    pathname-components
    pathname-default-host
    pathname-directory-path
    pathname-directory-string
    pathname-name-path
    pathname-name-string
    pathname-new-host
    pathname-relative?
    string->pathname
    symbol->pathname
    

  • pathname-default no longer accepts a host argument.
  • Representation of pathname directories changed to match Common Lisp. Directory is now either #f or a list of symbols and strings with first element either absolute or relative.
  • Unix pathnames now set device and version to unspecific. unspecific now means that the field is not used by the operating system.
  • Parsing rules for Unix filenames changed: the file type is the part of the name after the last dot, if any. If the dot occurs at the beginning or end of the filename, then it doesn't count -- in that case there is no type. Thus, names like `.' and `..' have no type.
• New Edwin features:

  M-x manual-entry
  M-x outline-mode
  M-x shell-resync-dirs
  M-x shell-command
  M-x shell-command-on-region
  M-x telnet
  RMAIL summary
  RMAIL sort
  REPL mode and asynchronous evaluation
  Printing commands
  "run light" for evaluation commands
  Reading and writing of compressed files (".Z" suffix)
  Reading and writing of encrypted files (".KY" suffix)
  Compress/uncompress commands for Dired
  Support for X protocols: WM_DELETE_WINDOW and WM_TAKE_FOCUS
  Time, load, and mail notification in mode line
  

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