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Comment by gsg | Hacker News Reader

Oops, breaks on empty files. I should have matched on the input_line chan in sum_channel to catch End_of_file - damn exceptions.

print_string should also be print_endline to match the original.

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Also, is doing flow control using exceptions an acceptable pattern in the OCaml world?

Like in Java:

  try {
     print(awesomeObj.getSomeState());
  } catch(NullPointerException npe) {
     awesomeObj = AwesomeObj.getInstance();
  }

would be considered very bad. You would instead be expected to do:

   if (awesomeObj == null) awesomeObj = AwesomeObj.getInstance();
   print(awesomeObj.getSomeState());

(how do you <code-wrap> stuff on here?)

Yes. Various parts of the stdlib are intended to be used by catching Not_found or End_of_file or whichever exception happens to be relevant.

It's not what I would have done.

(Mark text as code by putting it on a fresh line with two or more spaces in front. I don't think there is a way to do this inline.)

While being done in the standard library, several big libraries alternative (Core, Batteries...) prefer wrapping everything in an `option` type instead of raising an exception. Wrapping in an option avoids forgetting about catching the exception.

It's always weird to me when people talk about using exceptions for control flow.

Exceptions are, pretty much explicitly, a control flow mechanism. That's what they do, they transfer control from one place to another. It's like people are getting hung up on the name.

Exceptions, in Java land at least, are very costly (think interrupts and context switching). To do flow control using them is shooting yourself in the foot.

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