[Python-ideas] Transportable indent level markers. /// ; ; ; \\\

[Massimo Di Pierro]

I do not like it and I am not convinced this belongs to Python 

Yet you may like this other solution:

exec(reindent("def f(a):; x=0; for i in range(a):; x+=i; pass; return x; print f(5)"))

here reindent is a modification of the web2py reindent function (used in templates).

- ; is converted to \n
- loops are closed with pass
- ifs are also closed with pass
- def can be closed with pass or return
- class must also end with pass

In web2py-ese templates we would not use it like this. we would write instead:

{{def f(a):}}{{x=0}}{{for i in range(a):}}{{x+=i}}{{pass}}{{return x}}{{=f(5)}}

or break it into

{{
def f(a):
   x=0
   for i in range(a):
      x+=i
      pass
   return x
= f(5)
}} (indentation is irrelevant even within the {{code}})


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On Dec 12, 2011, at 4:07 PM, Ron Adam wrote:

> 
> While typing this reply to the "Alternate Suite Delineation Syntax For
> Python?" thread.  I realized that having things  all on a single line
> isn't important or needed!!!  Yes, it's not needed for templates, or
> code generation.  So this is an alternate to the alternate.
> 
> What is needed is a uniform way to represent indenting that is easy to
> transport to (ie paste into) code with different indent levels.
> 
> 
> INDENT LEVEL MARKERS:
> ----------------------
> Offer a new way to spell <indent+1>, <indent+0>, and <indent-1>.  
> 
> To make that work, we need to use unique character sequences that aren't
> already used.  After some thought, I came up with these indent-markers.
> 
>    ///   # indent level +1
>    ;;;   # indent level +0
>    \\\   # indent level -1
> 
> These are unique enough to be easy to see, and the tripled versions of
> them aren't really that bad as we already have triple quotes, and they
> would be less than the white space they are replacing in most cases.
> 
> So this isn't brackets, or braces. It would be just an alternate
> spelling in already valid python. It should not effect the parser,
> grammar, or interpreter in any way if it is done in pythons
> tokenizer.  :-)
> 
> 
> Reusing some previous examples.
> 
> #-----------------------
> 
>>   def acc(n) {: s=n; return {: def (i) {: nonlocal s; s += i; return
>> s}}}
> 
> #Standard python...
> 
> def acc(n):
>    s=n
>    def add(i):
>        nonlocal s
>        s += i
>        return s
>    return add
> 
> 
> #Single line version...
> 
>  def acc(n): /// s=n ;;; def add(i): /// nonlocal s \ 
>  ;;; s+=i ;;; return s \\\ return add
> 
> (The '\' character should still work.)
> 
> 
> #Transportable indent level version...
> 
> This could also be valid... and could be transportable to any other
> indent level without having to edit it.
> 
> (So would the above single line version by adding a ';;;' to the
> beginning.)
> 
> ;;; def acc(n):     # indent +0
> /// s = n           # indent +1
> ;;; def add(i):     # indent +0
> /// nonlocal s      # indent +1
> ;;; s += i          # indent +0
> ;;; return s        # indent +0
> \\\ return add      # indent -1
> 
> It has the nice properties of being uniform, and being able to be
> inserted easily into any existing code block without having to adjust
> the indent levels.
> 
> I believe that these properties are more important than being able to
> put things on a single line and could be a very useful in code
> generating programs. ;-)
> 
> 
> It may be easy to implement.
> 
> This could probably all be done in the tokinze.c get_tok() function,
> where it detects and converts white space to indention levels.  Nothing
> else in python would need to be changed.  The tokenizer already detects
> line continuations and different line endings, so this wouldn't be that
> out of place.
> 
> Cheers,
>   Ron
> 
> 
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