[erlang-questions] Re: implementing annotation in erlang
Fri Sep 11 18:37:17 CEST 2009
2009/9/9 paweł kamiński <>:
> finally I went through parse_transform but constructing even simple format
> from scratch is a nightmare.
> is there a way to construct code blocks in more elegant way, something like
> create_fun(LineNo, Name, Arity, Body, ..)-> would produce function block
> create_tuple(LineNo, Tuple)
> and so on
Whenever somebody tries to use parse_transform to implement some
problem which sounds easy (but then the complexity explodes), I tend
to immediately think about LFE - Lisp Flavoured Erlang. It worked for
me many times and I didn't have to bother with parse_transforms.
So, in LFE you could define a simple macro which would run your code
at compile time when you define a function. Eg. macro could add
function name to a well known ets.
It would be easy for you to do if you were exposed to any Lisp
already. If not, that's another paradigm shift to handle.
> and still Im thinking that extracting information from code in runtime is
> far more productive (elegant, sufficient, just simpler) then transforming
> code to something different. generally all I need is just to obtain
> information that this function is annoted with metadata and store that or
> make additional tasks. with parse transform I need to build and add new
> function to parsed module that other can call and get those information or
> create whole new file with well known name that other modules could refer
Erlang runtime is very simple and there you have only compiled modules
containing functions. Even the presence of variable bindings in a
shell is a hack.
As it may seem constraining for coders coming from other languages,
such simplicity makes robustness more easy.
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