[RFC] alternate exception handling method

[BCS]

The proposal:

   Provide a mechanism that allows for the in-place handling of exceptional 
cases. Rather than abandon the entire function call, when this mechanism is 
encountered, the runtime environment searches back through the call stack (much 
like with a normal throw) until it finds a handler and executes it and then 
returns execution to the place that the exception was raised. This could be used 
in cases where the exception case might be an error but not always or in cases 
where the problem can be fixed.

pros:
   Lightweight, no stack unwinding, could uses a global function ptr table.
   Allows for cheaper fix to fixable problems.
cons:
   Might be prone to abuse and or faulty use.
   Needs care that "fix" doesn't corrupt things.

   As I couldn't come up with any good keywords to use, I will give my examples 
with some somewhat humors choices. An exception handler for this type of 
exception will be called a "hammer", to raise one of these fixable exceptions 
use the keyword "nail".
   ("If the only tool you have is a hammer, every problem looks like a nail).


------------------

   // find the sample mean
   real SampleMean(SampleSet s)
   {
     if(0 == s.Number)                   // is there any data?
     {
       nail new SampleSet.NoSamples(s);  // try to fix the error
       assert(0 != s.Number);            // make shure it's fixed
     }

     return s.Sum/s.Number               // compute
   }


   ...

   try
   {
     writef("the mean is: ", SampleMean(i));  // try to print the mean
   }
   hammer(SampleSet.NoSamples e)              // if there is no data
   {
     e.Data.UpdateDataSet();                  // try to get more data
     if(0 == a.Data.Number)                   // check if we did
       throw Excption("Sorry, no data");      // if not, error
   }

   ...


------------------
Just a thought, if this waits till >1.0, oh well.