Re: [TCLCORE] TIP#329: Try/Catch/Finally syntax

[Twylite <tw...@cr...>]

Okay, I found some time to work on the reference implementation.

Changes:
- 'throw' has behavior consistent with 'error'.  The 'interp alias' 
approach that was suggested behaves weirdly if you don't get the 
arguments right, so the implementation is proc-based.
- removed the 'as {resultsVar optionsVar}' clause and introduced 
per-handler variable assignment
- improved error messages
- improved behavior of '-during'
- added tests (there are just under 100 tests covering most aspects of 
the functionality; more to come)

Outstanding issues:
- In the case of a fallthrough body "-", to which variable(s) should the 
outcome of the try body be assigned?
e.g.  try { throw FOO bar } trap FOO {em1 opts1} - trap BAR {em2 opts2} 
{ puts body }
It seems logical that the variables for the BAR case may be expected by 
the BAR body and should be set; but what about those for the FOO case?
Option #1: set the FOO case variables only; making sure the body works 
correctly is the developer's problem
Option #2: set the BAR case variables only; the fact that the FOO 
variables are left unset is a quirk of using the "-" syntax
Option #3: set the FOO and BAR variables; possibly more consistent from 
the developer's perspective, but adds complexity to any implementation 
that is aiming for performance
Option #4: sets the FOO and BAR variables as well as those of any other 
fallthrough cases in between, also at a cost in complexity/performance terms
The current implementation provides Option #2, but this is strictly a 
side-effect of the implementation and easily changed to #1 or #4 (#3 is 
a bit of a pain).
- Some corner cases around when "-during" should or should not be added 
to the options dict.

Updated version available at http://www.crypt.co.za/pub/try-2.tcl .

Regards,
Twylite