Re: Is Java useful for writing (C/C++) compiler

dale <dale@cs.rmit.edu.au> writes:


> I don't think it is all that clear at all. If you consider...
>
> while not End_Of_File (File) loop
> read file
> blah blah blah
> end loop;
>
> compared to
>
> begin
> loop
> read file
> blah blah blay
> end loop
> exception
> when End_Error =>
> null;
> end;


And our esteemed moderator says:


> [I would say the relative performance of the two loops depends entirely
> on how the compiler implements exceptions. -John]


Not really. The point is that *both* loops must raise End_Error on
End_Of_File. So in the first loop, End_Of_File is tested twice (once
explicitly, and once inside the implementation of "read file"),
whereas in the second loop, the explicit test is removed.


One can imagine an optimizing compiler that folds the two tests in the
first loop, into one test (especially if "read file" is inlined). But
(for sufficiently large files), the implementation of exception
raising/handling itself is irrelevant.


- Bob
[Indeed, but one can also imagine a simple-minded compiler that emits
explicit EOF testing code at the points where the exception might be
thrown. -John]

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