June 13
I have to modify preexisting code. As of now, the code fails and throws an exception at some point. I need to prevent the code from throwing(easy) but signal to the user of the code some notification(hard).

It would be cool if I could throw an exception as if the code yielded and it could be continued if I want.

simplified pseudoscope

void load()
{
  read(somefile);  <-- throws if somefile does not exist

  ...
}

goes in to

void load()
{
  try
  {
    file = read(somefile);  <-- throws if somefile does not exist
  }
  catch
  {
     file = null;
     throw new yeildException!4("File not found!");
  }

  yieldException!4:

  ...
}


then when one catches a yieldException somehow they can resume at the proper location to continue the function as if the exception never happened.

Because I don't have access to all the code nor do I want to rewrite large portions of it, it is impossible to redesign everything to make things work correctly.


I believe throw unwinds the stack which makes a yield semantic impossible?

I can't use a callback(too ugly and it would require modify huge amounts of code to add them everywhere unless it were global):


void load()
{
  try
  {
    file = read(somefile);  <-- throws if somefile does not exist
  }
  catch
  {
     file = null;
     userCallback("File not found!");
  }


  ...
}


Any devious D tricks that can be used to give the sort of yieldThrow I'm looking for?


BTW, if D had a yieldThrow which behaved like throw but saved the stack to rewind back to the point of yieldThrow, then one could simply do


void load()
{
  try
  {
    file = read(somefile);  <-- throws if somefile does not exist
  }
  catch
  {
     yieldThrow new yeildException!4("File not found!");
     // code returned back to this point when yieldThrow finished doing what it does.
     file = null;
  }


  ...
}


Remember, these errors occur inside some large processing(of a file) which might error depending on dependencies.  Some of these errors are not critical and I can't reparse the file each time because the same error will occur. I simply need to ignore the errors. I have access to the code where I can ignore them but I need some nice way to inform the user of the process that something didn't go as planed. Again, this wasn't defined in to the original code and it it already has it's own error handling.