Is there a straightforward way to convert an Erlang fun to a string? A call to io_lib:format only prints the function reference, e.g. something like "#Fun<erl_eval.20.67289768>". For example, I'd like to be able to do this:
1> Fun = fun() -> atom_to_list('hello world') end. 2> FunStr = fun_to_str(Fun). "fun() -> atom_to_list('hello world') end."
I'm looking for how to implement fun_to_str. In javascript, some interpreters have a .toSource() function that can be called on any object, including functions, that print their string representation. Any info is appreciated, thanks.
First, get the environment variables for the fun (which includes the abstract code):
1> {env, [{_, _, _, Abs}]} = erlang:fun_info(Fun, env). {env,[{[], {eval,#Fun<shell.21.83096281>}, {value,#Fun<shell.5.83096281>}, [{clause,1,[],[], [{call,1,{atom,1,atom_to_list},[{atom,1,hello_world}]}]}]}]}
Pretty print the abstract code using erl_pp:
3> Str = erl_pp:expr({'fun', 1, {clauses, Abs}}). [[[["fun", [[[[["()"]," ->"], ["\n ", [["atom_to_list",[[40,["'hello world'",41]]]]]]]]]]], [10,["end"]]]] 4> io:format([Str|"\n"]). fun() -> atom_to_list('hello world') end ok
(You have to add {'fun', 1, {clauses, ...}} around it to make it a complete Erlang expression)
You might be able to use erlang:fun_info/2 for that, atleast i get some information from the shell when doing
1> erlang:fun_info(fun() -> test,ok end, env). {env,[[], {value,#Fun<shell.7.37281544>}, {eval,#Fun<shell.24.85590193>}, [{clause,1,[],[],[{atom,1,test},{atom,1,ok}]}]]} 2>
You want the last list with the clause atom and then pretty print it using for instance erl_pp
