notes

module Try.Exceptions.Theory where

Exceptions

• Safe exception handling
  • Types of exceptions:
    • synchronous - generated in IO, thrown inside a single thread. Allow recovery and cleanup
    • asynchronous - generated from outside a thread. Allow cleanup, but no recovery
    • impure - generated in a pure code, thrown when a thunk gets evaluated.
      • Example: error
• [Exceptions and concurrency] - YT
  • use [safe-exceptions]

From Haskell in Depth (Chapter 7)

• Avoid using exceptions when possible
• Due to laziness, an exception in an expression doesn't happen until that expression gets evaluated.
• A thread can be killed by other threads or the runtime system (due to memory exhaustion, etc.)
• Types of exceptions:
  • programmable
    • used in pure monad stacks (e.g., ExceptT)
  • extensible
    • Extensions thrown anywhere, caught only in IO
    • Supported by the GHC runtime system
    • imprecise exceptions - thrown in pure code, order unspecified by the runtime system
    • All exceptions have an instance of Exception and are values of the SomeException type
• packages - exceptions, safe-exceptions