Python syntax in Lisp and Scheme

[Kenny Tilton]

Alex Martelli wrote:

> Kenny Tilton wrote:
> 
> 
>>Alex Martelli wrote:
>>
>>>... I do believe that the
>>>divergence problem has more to do with human nature and sociology, and
>>>that putting in a language features that encourage groups and subgroups
>>>of users to diverge that language ....
>>
>>Can someone write a nifty Python hack to figure out how many times
>>Lispniks have tried to get Alex to explain how macros are any different
>>than high-order functions or new classes when it comes to The Divergence
>>Problem? I love that we have given it a name, by the way.
> 
> 
> The very 'feature' that was touted by Erann Gat as macros' killer advantage
> in the WITH-CONDITION-MAINTAINED example he posted is the crucial
> difference: functions (HO or not) and classes only group some existing code
> and data; macros can generate new code based on examining, and presumably to
> some level *understanding*, a LOT of very deep things about the code 
> arguments they're given.  

Stop, your scaring me. You mean to say there are macros out there whose 
output/behavior I cannot predict? And I am using them in a context where 
I need to know what the behavior will be? What is wrong with me? And 
what sort of non-deterministic macros are these, that go out and make 
their own conclusions about what I meant in some way not documeted?

I think the objection to macros has at this point been painted into a 
very small corner.


> ...If all you do with your macros is what you could
> do with HOF's, it's silly to have macros in addition to HOF's 

There is one c.l.l. denizen/guru who agrees with you. I believe his 
position is "evrything can be done with lambda". And indeed, many a 
groovy WITHOUT-CELL-DEPENDENCY expands straight into:

    (call-with-cell-dependency (lambda () ,yadayadayada))

But code with WITHOUT-CELL-DEPENDENCY looks prettier (I hope we can 
agree that that matters, esp. if you are a Pythonista).

-- just
> MTOWTDItis encouraging multiple different approaches to solve any given 
> problem -- this, of course, in turn breeds divergence when compared to a
> situation in which just one approach is encouraged.  If you do use the 
> potential implied in that example from Gat, to do things that functions and 
> classes just couldn't _begin_ to, it's worse -- then you're really 
> designing your own private divergent language (which most posters from
> the Lisp camp appear to assert is an unalloyed good, although admittedly
> far from all).  This is far from the first time I'm explaining this, btw.

Oh. OK, now that you mention it I have been skimming lately.

> 
>>One popular macro is WITH-OUTPUT-TO-FILE. My budding RoboCup starter kit
>>was a vital WITH-STD-ATTEMPT macro. Oh god, no! I need to see the ANSI
> 
> 
> Do they do things a HOF or class could do? 

Yes.

>... If so why bother using such
> an over-powered tool as macros instead of HOFs or classes?  

Hang on, we just agreed that in this case the only added value is 
prettier code. Nothing over-powered going on. (And that is, in this 
case, why I bother.)

-- 
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