Could Emacs be rewritten in Python?

[Alex Martelli]

Michael Hudson wrote:

> Alexander Schmolck <a.schmolck at gmx.net> writes:
> 
>> > Requiring declarations of all variables would be a HUGE change to
>> > Python, IMHO.
>> 
>> Sure and I'm in no way arguing for such a change (and neither Paul
>> Foley who, unlike me, considers implicit declaration a major
>> flaw). I just don't understand why it would "unfeasible
>> syntactically" -- *syntactically* it seems quite unproblematic to
>> me.
> 
> Well, maybe I should have been more clear than just "syntactically" --
> but you do understand what I mean, no?  I don't think you can
> distingusish establishment and mutation of bindings in Python without
> significant damage to the "feel" of the language.

I think you COULD choose to add to Python two special assignment
delimiters -- say := and ~= for definiteness -- with semantics as
follows:

    <name> := <expression>
    
        if <name> was previously unbound in this scope, bind it;
        if <name> was already bound, raise an exception.


    <name> ~= <expression>

        if <name> was already bound in this scope, re-bind it;
        if <name> was previously unbound, raise an exception.

while leaving good old = to mean exactly what it means today.

Would such additions "significantly damage the feel of the
language"?  I don't know.  I doubt they'd add any important
expressiveness, or see any significant use; therefore, in
practice, I think they'd remain obscure, rarely-used "dusty
corners of the language" and thereby indirectly do some
damage (complexity not pulling its weight).  But I don't see
any sense in which these difficulties could possibly be
described as "syntactical", even lato sensu.


Alex