[Tutor] call a def/class by reference

[DS]

Alan G wrote:

>> I'm actually pretty surprised that there isn't a built-in facility with
>> Python for referencing functions like this.
>
>
> I'm not. In fact its pretty unusual in any language to try to map
> from function name to function directly. Dictionaries are the
> universal solution for this, I can only think of a handful(4?)
> languages that I've used (Out of 20 plus) that can do
> string -> function mapping directly.
>
> Its not usually a very useful thing to do - how would the
> typical user know what the function names were? Either the
> user has access to the code or the code presents the names
> to the user(as strings) in which case a mapping has to
> exist somewhere already.
>
> I'm curious as to how you are addressing those issues?
> Is this something that only developers will be using?
> How will the user know what names are possible?
>
> Alan G.


I am playing with building a facility that accepts equations or
expressions that are parsed and solved.  I hope to use this with genetic
algorithms that would create mostly useless expressions, but that over
time might become better.  If I was doing it for users building
expressions, I'd probably do a javascript kind of approach for
assembling expressions from lists.  Your point is well taken, because
I'm often awed at the amazing ly stupid errors that I make when I'm
typing. 

Rest assured, I don't know 20 languages, computer or otherwise.  I know
that I used some sort of thing like that in the 80's with Revelation, a
database/language derived from Pick.  (That one is probably a little
obscure, it may not be on your list of 20).  I also think you can do
that in Perl, but bear in mind I know less about Perl than I do Python.

ds