[erlang-questions] type syntax question
Thu Oct 30 09:05:44 CET 2008
Anthony Shipman wrote:
> I want to write something like
> -type (deviceOpHandler() :: fun( (integer(), cstate()) -> cstate() )).
> -spec (okHandler/2 :: deviceOpHandler()).
> okHandler(_DeviceID, CState) ->
> sendResponse(200, "OK", CState).
> but I can't find the right combination of parentheses to please the compiler.
> Is this kind of specification possible?
The deviceOpHandler() does not need a "type" declaration. In fact, it
shouldn't have one for just the above. In the old spec syntax, the
above example can simply be written as:
-spec(okHandler/2 :: (integer(), cstate()) -> cstate()).
or, from R12B-4 onwards, more simply as:
-spec okHandler(integer(), cstate()) -> cstate().
which is now the recommended way -- the EEP needs to be updated.
If at some other function you need to specify that the function takes a
deviceOpHandler as an argument, then you can define that type as:
-type deviceOpHandler() :: fun((integer(), cstate()) -> cstate()).
and use it as:
-spec my_foo(deviceOpHandler()) -> 42.
> Will there be documentation on the type and spec syntax coming soon?
Well, the answer depends on your definition of "soon"... ;-)
The current plan is that types & specs will be properly documented in R13.
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