[slang-users] slang 2 exception class hierarchy

["John E. Davis" <davis@xxxxxxxxxxxxx>]

Hi,

Before releasing a slang2 snapshot, I would like your opinion on slang
2's exception class hierarchy.  This question is not necessarily
geared only at those using the interpreter since any app using the
library can add new exception classes to the tree via the
SLerr_new_exception function.

The proposed (and implemented) exception class hierarchy is as follows:

    AnyError
      OSError
         MallocError
      InternalError
      ParseError
         SyntaxError
         DuplicateDefinitionError
         UndefinedNameError
      RunTimeError
         IOError
             WriteError
             ReadError
             OpenError
         ImportError
         InvalidParmError
         TypeMismatchError
         UserBreakError
         StackError
             StackOverflowError
             StackUnderflowError
         ReadOnlyError
         VariableUnitializedError
         NumArgsError
         IndexError
         UsageError
         ApplicationError
         NotImplementedError
         LimitExceededError
         MathError
            DivideByZeroError
            ArithOverflowError
            ArithUnderflowError
         DataError
         UnicodeError
            InvalidUTF8Error
         UnknownError

The indentation shows that e.g., MathError is a subclass of
RunTimeError, which itself is a subclass of AnyError.

I have mixed feelings regarding the placement of ImportError.  It can
certainly occur during runtime, but one might also think of it as an
OSError or an IOError.

Any thoughts?

Thanks,
--John

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