The source code for Tcl is managed by fossil. Tcl developers coordinate all
changes to the Tcl source code at
> [Tcl Source Code](https://core.tcl-lang.org/tcl/timeline)
Release Tcl 8.7b1 arises from the check-in with tag core-8.7-b1.
Highlighted differences between Tcl 8.7 and Tcl 8.6 are summarized below,
with focus on changes important to programmers using the Tcl library and
writing Tcl scripts.
## Internationalization of text
- Full Unicode range of codepoints
- New encodings: utf-16/utf-32/ucs-2(le|be), CESU-8, etc.
- `encoding` options -profile, -failindex manage encoding of I/O.
- `msgcat` supports custom locale search list
- `source` defaults to -encoding utf-8
## Zip filesystems and attached archives.
## Unix notifiers available using epoll() or kqueue()
- relieves limits on file descriptors imposed by legacy select()
## Notable incompatibilities
- No --disable-threads build option. Always thread-enabled.
- Windows platform needs Windows 7 or Windows Server 2008 R2 or later
## New commands
- `array default`, `array for`
- `chan isbinary`
- `coroinject`, `coroprobe`
- `clock add weekdays`
- `dict getwithdefault`
- `file tempdir`, `file home`, `file tildeexpand`
- `info commandtype`
- `ledit`
- `lpop`
- `lremove`
- `lseq`
- `package files`
- `string insert`, `string is dict`
- `tcl::process`
- `*::build-info`
- `readFile`, `writeFile`, `foreachLine`
## New command options
- `clock scan ... -validate ...`
- `info loaded ... ?prefix?`
- `lsearch ... -stride ...`
- `regsub ... -command ...`
- `socket ... -nodelay ... -keepalive ...`
- `vwait` controlled by several new options
## Numbers
- 0dNNNN format to compel decimal interpretation.
- NN_NNN_NNN, underscores in numbers for optional readability
- Functions: isinf() isnan() isnormal() issubnormal() isunordered()
- `fpclassify`
- Function int() no longer truncates to word size
## tcl::oo facilities
- private variable and methods
- `method -export`, `method -unexport`
