Python syntax in Lisp and Scheme

[Joe Marshall]

Alexander Schmolck <a.schmolck at gmx.net> writes:

> prunesquallor at comcast.net writes:
>
>> mike420 at ziplip.com writes:
>> 
>> > I think everyone who used Python will agree that its syntax is
>> > the best thing going for it. 
>> 
>> I've used Python.  I don't agree.
>
> I'd be interested to hear your reasons. *If* you take the sharp distinction
> that python draws between statements and expressions as a given, then python's
> syntax, in particular the choice to use indentation for block structure, seems
> to me to be the best choice among what's currently on offer (i.e. I'd claim
> that python's syntax is objectively much better than that of the C and Pascal
> descendants -- comparisons with smalltalk, prolog or lisp OTOH are an entirely
> different matter).

(I'm ignoring the followup-to because I don't read comp.lang.python)

Indentation-based grouping introduces a context-sensitive element into
the grammar at a very fundamental level.  Although conceptually a
block is indented relative to the containing block, the reality of the
situation is that the lines in the file are indented relative to the
left margin.  So every line in a block doesn't encode just its depth
relative to the immediately surrounding context, but its absolute
depth relative to the global context.  Additionally, each line encodes
this information independently of the other lines that logically
belong with it, and we all know that when some data is encoded in one
place may be wrong, but it is never inconsistent.

There is yet one more problem.  The various levels of indentation
encode different things: the first level might indicate that it is
part of a function definition, the second that it is part of a FOR
loop, etc.  So on any line, the leading whitespace may indicate all
sorts of context-relevant information.  Yet the visual representation
is not only identical between all of these, it cannot even be
displayed.

Is this worse than C, Pascal, etc.?  I don't know.  
Worse than Lisp, Forth, or Smalltalk?  Yes.