[erlang-questions] idea: function meta data

Andreas Hillqvist <>
Thu Nov 15 15:31:31 CET 2007


I like the Idea of function meta data.

But it might be better/simpler/easier/harder to use an alternativ
prefix, like double -- (Similar to %, %% and %%%).

Why not use the name atom instead of meta?
To me meta dose not contribute with value to the syntax.

Would look like:

    -module(test).
    -export([fac/1].

    --doc("the factorial function").
    --type("int -> int").
    --keywords([math]).
    fac(0) -> 1;
    fac(N) -> N*fac(N-1)

Or some other prefix like "+"(Just an example, Do not like + myself.
To much alike the udiff format. ;-)?
    -module(test).
    -export([fac/1].

    +doc("the factorial function").
    +type("int -> int").
    +keywords([math]).

    fac(0) -> 1;
    fac(N) -> N*fac(N-1)


Regards
Andreas Hillqvist

2007/11/15, Joe Armstrong <>:
> Module have metadata  Mod:module_info(export) etc.
>
> But functions do not.
>
> idea - attach function meta data with a new attribute.
>
>      -meta(doc, "the factorial function").
>      -meta(type, "int -> int").
>      -meta(keywords, [math]).
>
>      fac(0) -> 1;
>      fac(N) -> N*fac(N-1)
>
> The meta data gets *attached* to the Next function in the module
>
>     -meta(process, true).
>     foo() -> spawn(fun() -> ... end)
>
> After compilation meta data can be access as follows:
>
>    Mod:meta_data(fac, 1, doc) => "the factorial function"
>    ...
>    Mod:meta_data(fac, 1, glurk) => '$nothing'
>
> if we then *standardise* the meta data it will be easy to make loads
> of nice tools for type checking, documentation etc.
>
> I'm off on a trip today - so can somebody hack the preprocess and
> parser to do this? (( this needs a small change
> attributes have a different syntax and must be at *before* all functions))
>
> This adds introspection to the language !
>
> /Joe Armstrong
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