use strings to call functions

[Klaus Neuner]

>
> A file extension is not necessarily 3 chars long.

No, of course not. But it is, if I choose to use only (self-made) file
endings that are 3 chars long. Anyway, it was just an example.

> handlers = {
>     ".txt" : handle_txt,
>     ".py" : handle_py,
>     # etc
>     }
>

That is exactly what I would like to avoid: Having to map the function
'handle_txt' to '.txt'. Firstly, because I don't want to repeat
anything and secondly, because I will one day add a new function and
forget to add its name to the dictionary. (This is not severe if there
is only one dictionary for mapping functions, but it will make life a
lot harder, if a lot of mappings of this kind are used.)

What I want is calling the string directly. In Prolog, I would use
something like:

get_file_ending(File, Ending),
Predicate =.. [Ending, File],
call(Predicate).