Slide section from the Tcl 2012 State of Tcl talk that goes over the changes in Tcl 8.6 in point friendly format.

1. Tcl/Tk 8.6
Current development branch (or 9.0?)
In final release candidates right now
8.6a1 development initiated April 2008
Same month of 8.4.19 release
8.6b1 released December 2008
8.6b2 released August 2011
8.6b3 released September 2012
8.6.0 in RC now

2. Tcl/Tk 8.6 TIPs
Numerous TIPs implemented for 8.6
65 TIPs Final
+14 from 2011; +3 previous year
+1 also in 8.5.11 (tk_getSaveFile change)
1 more in accepted state (T399)
5 more in Draft state (3 redundant or out-dated)
81 TIPs targeting 8.7 (in Draft state)
3 more already Withdrawn
+9 from 2011; +5 previous year
7 TIPs targeting 9.0 (in Draft state)
+0 since 2010
1 withdrawn, 1 rejected

3. Tcl 8.6 OO
Core OO! (T257 T320 T354 T380
T381 T397) % oo::class create example {
variable foo
Foundational OO system constructor {{value 10}} {
inspired by XOTcl and snit set foo 0
my bar $value
Provided in core (no package) }
destructor { }
oo::class, oo::define, oo::copy, method bar {input} {
oo::object, ... incr foo $input
}
Class-based object system with }
=> ::example
dynamic redefinition allowed % example create b 4
Per-object customization with => ::b
% b bar 3
filters, mixins and more => 7
Has C API to create and
manage classes, instances and
methods

4. Tcl 8.6 NRE
New non-recursive bytecode engine
Less stack hammering (aka stackless)
Proper tailcalls (T327)
Enables coroutines, aka generators
coroutine, info coroutine, yield (T328)
Symmetric coroutines, multiples args, yieldto (T396)
tcl::unsupported::yieldTo/yieldm
Coroutines still in development
C API to allow user commands to be restartable
Tcl_NR* (T322 T353 T356)
Not all Tcl commands can yield

5. Tcl 8.6 string handling
Simplified Tcl prefix matching (T195)
tcl::prefix, with C API for option parsing (T265)
Unicode aware string is space/trim* (T318
T413)
BOM and zero-width spaces added
New string is entier (T395)
Number of any size (accounts for bignums)

6. Tcl 8.6 list handling
Find insertion point in sorted list lsearch -bisect
(T313)
Grouped sort with lsort -stride (T326)
Great for use with array get or dict output
Allow lset to extend lists (T331)
lset myList end+1 foo equivalent to lappend myList foo
Collecting loops with lmap and dict map (T405)
Simplified (and faster) than foreach or apply
set good [lmap x $vals {expr {[isGood $x] ? $x : [continue]}}]

7. Tcl 8.6 interp and namespace
Ability to cancel script evaluation (T285)
interp cancel, C API helper Tcl_CancelEval
Check if interp is active Tcl_InterpActive (T335)
namespace ensemble create -parameters (T314)
encoding system at startup is iso8859-1, not
identity
info errorstack, -errorstack return dict (T348)
tcl::unsupported::representation
Get Tcl_Obj internal rep

8. Tcl 8.6 extras
New binary encode|decode with base64 (T317)
binary is now a namespace ensemble
Base-2 support in format and scan with %b (T343)
dict filter takes multiple patterns args (T341)
Windows registry has 64-bit support (T362)
Added tcl_platform(pathSeparator) key (T315)
For $::env(PATH), not file paths (use file)
Unicode literals past the BMP (T388)
load adds -global and -lazy options (T416)

9. More 8.6 stuff!
More commands take no args gracefully (T323)
Reduce non-essential error cases, good with {*}
New try/finally syntax (T329) set f [open $file a]
try {
try body ?handler...? ?finally script?
puts $f "oops ..."
throw type message # ...
Alternative to error } finally {
close $f
}
try {
set f [open $file]
} trap {POSIX EISDIR} {} {
puts "failed to open $file: it's a directory"
} trap {POSIX ENOENT} {} {
puts "failed to open $file: it doesn't exist"
}

10. Tcl 8.6 files and channels
New file tempfile ?nameVar? ?template?
Creates tempfile and returns a channel (T210)
Enhanced chan command
close can close only read or write side (T332)
Anonymous pipes with chan pipe (T304)
Tcl level channel transformations chan push|pop (T230)
IPv6 support in socket (T162)
Currently uses OS preference for AF selection
Exit quickly with non-blocking block channels (T398)

11. But wait, there’s more!
Zlib compression included with new core zlib
command (T234 T400)
Builds on standard zlib sources
Full zip and unzip support for gzip and zlib formats
Supports channel streaming for transforms
Includes adler32 and crc32 checksumming
Includes Tcl_Zlib* C API

12. And on the C side of 8.6
Make Tcl_Interp more opaque
No more interp->result (T330)
Use Tcl_GetStringResult(interp) instead
API for interp->errorLine (T336)
Tcl_Get|SetErrorLine
Access to startup scripts from C (T338)
Tcl_Obj *Tcl_GetStartupScript(const char **encodingNamePtr)
void Tcl_SetStartupScript(Tcl_Obj *pathPtr, const char *encodingName)
Exported Tcl_TransferResult (T307)
Portable Tcl_StatBuf access (T316)
Tcl_Get*FromStat
New Tcl_BackgroundException for bgerror (T337)

13. More 8.6 Under the Hood
Exported library loading functions (T357)
Tcl_LoadFile, Tcl_FindSymbol, Tcl_FSUnloadFile
Windows moving to full -DUNICODE build
Supports Windows XP or later
OS X moving to Cocoa
Supports OS X 10.5 or later, allows 64-bit builds
Next version of [incr Tcl] (v4) uses TclOO
Thread extension to be included with core sources
Thread builds (--enable-threads) now default (T364)
Several other extensions included too

14. Tcl 8.6 TDBC
Standard interface for database connectors (T308)
Currently has drivers for sqlite, mysql, odbc and postgres
Leverages TclOO framework
package require tdbc::sqlite3 db transaction {
tdbc::sqlite3::connection create set firstname "Fred"
db "phonebook.sqlite3" set lastname "Flintstone"
set statement [db prepare { $statement foreach row {
SELECT phone_num FROM directory puts [dict get $row phone_num]
}
WHERE first_name = :firstname
}
AND last_name = :lastname
}] $statement close
db close

15. Tk 8.6 Features
Windows Vista/7 theme support for Ttk
Backported to 8.5.8
Updated mouse-wheel behavior (T171)
Tk OS X Cocoa
Enables 64-bit builds
Requires OS X 10.5+
Available for Tk 8.5
New canvas features
Absolute canvas item positioning (T236)
Canvas item vertex editing (T97)
Angled text items (T119)

16. Tk 8.6 font dialog
Uses native dialog on Windows, OS X (T324)
% tk fontchooser show
% tk fontchooser configure
-parent . -title {} -font {{Gill Sans} 12 bold roman}
-command {} -visible 1

17. Tk 8.6 PNG support
Full PNG support with compression (T244)
Leverages zlib support
image create photo -file ouster.png
-format "png -alpha 0.5"

18. Tk 8.6 extras
New tk busy adapted from BLT’s busy (T321)
User can generate <Focus*> events
Unfocussed text insertion cursor control (T197)
GIF image writing uses LZW compression
wm attributes -type on X11 (T359)
Modernized X11 menus (T360)
Web colors for Tk (T403)
New ttk::spinbox widget (also in 8.5.9)
Consider the alternate widgets combobox and menubutton

19. In summary ...
8.5 is 99% compatible with 8.4 at Tcl level
Over 100 new features for developers
Stable and ready for all task loads
Slightly slower than 8.4
8.6 currently in final RC
Final release date: taking bets!
Lots of new features
Slightly slower than 8.5, performance wasn’t a focus
Further discussion at the conference
Tcl Dev Kit and Komodo support both 8.5 and 8.6
Final 8.6 will require further an update