[erlang-questions] alternative syntax to '-spec' attributes.

Eric Merrit <>
Tue Jan 29 01:49:32 CET 2013

There seems to be an alternative syntax for specs. Lets say we have a spec declared in the traditional way

-spec to_boolean(term()) -> boolean().

We could also declare it the following way and have it be consumed without problems

-spec to_boolean/1 :: (term()) -> boolean().

I like the second way quite a bit since it visually distinguishes between spec declarations and function declarations better then the traditional syntax. However, I recently went looking for documentation on this and now can't find it. So I am wondering what its status is.


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