Question

I’ve been scrounging around the web looking for various typing practices of Erlang programs and there seem to be a few… although its somewhat difficult to find a solid source of info namely Im looking for practical info about:

1.-specs – this one looks pretty attractive. a few places mention that the functions that have an associated -specs directive with it are checked at compile time(for correct type usage)… I cant seem to find more info on how to use it (which tool to use – Dialyzer,TypEr?). Im really eager to create a small parser/code-gen that would generate these ‘specs’ from function declarations of the form

functionName(param1 :List, param2 :Tuple) -> ... 

I have not seen if -spec supports abstract types (user declared types – ‘Car’ type –

{car,{weight,_},{height,_},{maxSpeed,_}} 

2.-deftype directive mentioned here

Erlang would become so much more powerful for me, if I could start typing things and have them be checked at compile time. The run-time the parser/code-gen I mentioned above would generate guard type checks in the output source-code.

Answer 1

More info on the type and spec attributes here:

http://www.erlang.org/eeps/eep-0008.html

Dialyzer can be used to check them (see dialyzer --help).

Typer can be used to generate them (see typer --help).