[erlang-questions] Why doesn't Erlang has return statement?
Richard A. O'Keefe
Thu Dec 18 03:40:03 CET 2014
Let me offer one example of how ‘return’ can affect things.
Suppose I have a function
Now suppose I discover that this is sometimes returning integers
and sometimes returning floats, but my life would be easier if
it always returned floats. Easy:
I don’t have to look inside <|stuff|> at all. Any value returned
will be caught this way. But in the presence of ‘return’, I have
to locate each and every ‘return’ and patch that separately.
Yes, I have had to do this kind of thing in C. I am actually
quite tired of writing
#define safely(e) (void)(<|clean up|>), e
macros and changing
and then finding I’ve missed one. This is of course why
Lisp provides unwind-protect, which Java copied as
What is the price of NOT having return?
Code duplication in a few rare cases.
case E1 of P1 -> .., ^E2 ; P2 -> .., ^E3 ; P3 -> .. ; P4 -> .. end, E5
has to become
case E1 of P1 -> .., E2 ; P2 -> .., E3 ; P3 -> .., E5 ; P4 -> .., E5 end
A compiler that does cross-jumping optimisation can eliminate the
duplication in the BEAM code.
If you keep your function bodies small, a little bit of duplication
won’t be a problem. (Is Garrett Smith reading this thread?)
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