Why not allow empty code blocks?

[Rustom Mody]

On Sunday, July 31, 2016 at 7:07:45 AM UTC+5:30, Gregory Ewing wrote:
> Michael Torrie wrote:
> > Python would have been alright to teach "programming," but to
> > teach the actual theory of programming languages (lambda calculus, lists
> > as a foundation unit for all other data structures)
> 
> I wouldn't say that "lists as a foundation unit for all other
> data structures" is (or should be) part of the fundamental theory
> of programming languages.
> 
> It seems to me that Python's notions of sequences and mappings
> are much more general and elegant theoretical elements to build
> on.

A key component of a fundamental theory of computation is the idea of
a universal data structure.

For a turing machine its the tape that can carry data or another TM to make
a UTM (UNIVERSAL turing machine)

For a von Neumann machine its the memory that is impartial to whether its 
holding data or code  (as against Harvard architecture)
https://en.wikipedia.org/wiki/Harvard_architecture#Contrast_with_von_Neumann_architectures

For Gödel's theorem it is humonguous integers which can ‘carry’ plain ol’ 
integers or theorems, proofs and effectively ‘the whole world’ via the
Gödel-numbering:
https://en.wikipedia.org/wiki/G%C3%B6del_numbering

At the other end of the spectrum is Lisp whose S-expression is likewise
universal and can be effectively used for carrying the whole theory much more
elegantly than Turing more elegantly than Gödel:
http://www.diku.dk/~neil/comp2book2007/book-whole.pdf

>From a software engineering pov, yes one can encode any data structure as
arbitrary length integers. It works as data structure but its a horrible.
This is the Gödel approach

By cutting up the humonguous number into small squares on a tape, Turing’s 
approach is more tractable. Its still clumsy because it requires parsing.

Structure the tape as a tree and this nuisance vanishes.
This Lisp/S-exp/Neil-Jones cleanest of all solutions is like everything else in
our field least known.

Of course one could argue that mapping is somehow more universal than list.
[I have often pondered this question]
ie one can represent
[a,b,c]
as
{0:a, 1:b, 2:c}

Still, whatever is chosen, one needs one single data structure (or more 
correctly data type) to carry the whole world.

Lists PLUS Mappings will not do

[Note I am not talking software engineering but requirements for a complete theory]