[erlang-questions] Newbie: Is there a short-circuit for the comma operator?
Wed Oct 10 08:53:16 CEST 2007
Nope. Such a thing does not exist.
But it seems you want to do something that is well suited for throw/1.
try begin Exp1, Exp2, Exp3, Exp4 end of
V -> V % Return value from Exp4
catch X ->
X % Value from embedded throw/1
If any of ExpN evaluates throw(done),
the catch clause is evaluated with X bound to 'done'.
See also the Erts Reference manual.
On Wed, Oct 10, 2007 at 07:14:11PM +1300, James Cone wrote:
> Hello All,
> This isn't explicit in the Erlang Reference Manual (v5.5.5), so you may
> not think of it this way:
> There is (something morally equivalent to) an operator ",", which is the
> lowest priority of all operators, and the evaluation of
> exp1, exp2
> - have all of the side-effects of exp1
> - have all of the side-effects of exp2
> - return the value of exp2
> 15> 0, 1.
> Is there an operator or function that short-circuits the comma operator,
> so if exp1 uses it, exp2 will not be evaluated?
> eg (supposing it's called return, which is the name of the equivalent
> operator in C)
> > if 1==0 -> -1; true -> return 0 end, 1.
> I want this because I have a function with some deeply nested tests, and
> I want to tail-recurse from only some of the cases, without copying all
> of the following expressions (after a comma operator) into all of the
> other cases.
> Am I making sense? Does such a thing exist?
> erlang-questions mailing list
/ Raimo Niskanen, Erlang/OTP, Ericsson AB
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