Missed the WAT thread, so here's one for intentionally cursed code

Offtopic
21

I hate/love this so much.

To the list it goes.

22

Fantastic thread

23

To expand on this, another angle is that without else rethrow(), Julia’s bare catch “falls back” to continuing after a if-elseif exception type block. One could argue this is equally valid default behavior, like returning nothing for the “cursed” sqrt_second, but PEP8 argues:

A bare except: clause will catch SystemExit and KeyboardInterrupt exceptions, making it harder to interrupt a program with Control-C, and can disguise other problems. If you want to catch all exceptions that signal program errors, use except Exception: (bare except is equivalent to except BaseException: ).

To explain BaseException, PEP352 introduced another layer of hierarchy to separate some lower-level exceptions from the run-of-the-mill Exception superclass in case the user does want generic handling of the latter; I wouldn’t call except Exception: default behavior because a subset is specified. I don’t know if there’s something similar in Julia, but we wouldn’t need to change our flatter Exception hierarchy with an extra defined supertype because we have Union.

BaseException # Julia’s equivalent is just called Exception
├── BaseExceptionGroup
├── GeneratorExit
├── KeyboardInterrupt
├── SystemExit
└── Exception
… …├── …

I personally agree that Control-C should simply stop the program unless InterruptException is specifically handled, so rethrowing makes more sense as a default behavior for caught exceptions over continuing. Here’s an example where the InterruptException gets caught and risks continuing:

function foo(t=3.0) # t gives time to Control-C
  try
    sleep(t) # Control-C gets caught
    div(1,0)
  catch
    println("catching...")
    sleep(t) # now Control-C stops the program
  end
  "foo end"
end
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