[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 known as ''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

(TBC)

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