[MS] every now and then I trip on some things in the core that I'd like to change and can't. This page is meant to keep a list, additions welcome.

The first batch concerns command invocation:

   * get rid of '''TCL_ALLOW_EXCEPTIONS''': the library shouldn't care about that and always return the actual code; '''tclsh''''s main can do whatever it needs, of course. This functionality seems to have fallen on the wrong side of the border.
   * of course .... '''iPtr->result''' should die!
   * stop promising that a command receives an '''empty unshared result''' in the interpreter: a command has to set its result from scratch, reset it or leave it untouched. This has performance implications, but also enables simpler shell-style pipelining (without nesting [[...]]). Maybe reserve a variable or have a command to get the interp's result.
   * '''Tcl_[[GS]]etCommandInfo''' and direct calling of commands!! At least rethink thoroughly 

Other things
   * hide more implementation details behind '''opaque pointers''': interp, CallFrame (don't let anybody else alloc them, they do not need to know the size nor how the core allocates or frees them), ...
   * change '''Rule [[1]]''' in [Tcl.n]: let the command be identified after substituting the first word but before substituting the rest. This allows completely bugfree compilation
''Do you mean''
  proc foo {x y} {expr {2*$x}}
  foo 3 [proc foo {x y} {return 2$x}]
''should return 6 rather than 23 as it currently does?''

Precisely! Maybe a better illustration: look at this currently unsolvable (at reasonable cost) ''bug'':
======
mig@oli:~$ tclsh
% set x 1[proc set args {puts AHA!}]
1
mig@oli:~$ tclsh
% eval {set x 1[proc set args {puts AHA!}]}
AHA!
======
(Note that that's 8.5, 8.6 may require a different example to show the effect)

   * change '''Rule [[1]]''' in [Tcl.n]: let the first word be not a ''command'' but a ''[command prefix]'' (aka ''autoexpand first word''). Note that this makes it difficult to deal with commands with names that are not proper lists (eg ''foo{bar}'') or that have spaces: they have to be [[list]]-protected


[ferrieux] If you allow my $.02, an old dream of mine: '''ease polymorphism of Tcl_ObjType's'''. Currently plenty of code checks pointer equality with &someObjType: that's a braindead version of OO programming; this is all the more surprising that the spirit of the implementation is otherwise adequately OO (function pointers). One corollary would be to rip off the List object type's special status (under performance constraints though), so that it becomes easily sub-classable. Maybe a more important one: make it possible for an extension to subclass predefined types.

[MS] Ah yes ... that reminds me:
   * change the name '''Tcl_Obj''' to '''Tcl_Value''' (and drop the old one); or '''Tcl_Thing''' ... or anything that does not suggest OO 
(TBC)

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