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fjh@munta.cs.mu.OZ.AU (Fergus Henderson) replied:
> I'm not familiar with Python, but I'm familiar with Haskell, which also
> uses whitespace to structure code.
> 
> >linewrap,
> 
> This is not a problem in Haskell; you just need to make sure that
> you indent the wrapped part of the line, e.g.

The point is that numerous text editors, word-processing packages,
mail-handling systems can and do automatically line-wrap, and can thus
corrupt such programs, and such things don't know the rules for Haskell,
but always happen to respect the normal notions of whitespace (ie that
any amount of whitespace is equivalent to any other amount of
whitespace). 
> 
> 	this is a very long statement of pseudo-haskell that doesn't quite
> 		fit on one line
> 
> >tabs,
> 
> So disallow them!
Again this just makes life difficult when you encounter software that
replaces spaces by tabs automatically.

> 
> >painful to automatically generate code,
> 
> In Haskell it is not painful to automatically generate code, because
> Haskell does not *require* the use of layout to indicate nesting;
> curly braces and semicolons can be used instead.  You can also
> mix the use of implicit nesting (via layout) and explicit nesting
> (via curly braces and semicolons).

Well that's my point, that using the conventional notion of language
as a symbol-sequence, and deploying bracketing constructs, is more
powerful and useful than trying to treat sourcecode as a 2-D array of
fixed-width characters.

> 
> >virtually impossible to stream-edit code,
> 
> Huh?  Why?
OK, how do you automatically merge diff's?   Or paste in a common
piece of code at several different places where the indentation might
happen to be different?

> >proportional fonts,
> 
> Even proportional fonts don't have proportional whitespace!
But proportional-font display techniques don't always respect them,
and usually the spaces are so narrow (especially in san-serif styles)
that you can't be sure just be looking if two lines start with the
same number.

[long list of detailed counter-arguments omitted]

People are used to the notion of programming (and natural) languages
being relatively context-free, and having the _invisible_ whitespace
at the start of each line as an unnecessary context-sensitive feature
can be a real pain and source of confusion, error and bugs.  It breaks
referencial transparency for one thing.  It's the sort of mistake
that's been made before, in the days of punched cards, Fortran and
Cobol, before enough people understood grammar theory.

There really is no difficulty at all in parsing a normal block-
structured language and formatting it in a suitably indented form, and
you get all the benefits of being able to cut/paste without worry, as
well as the benefit of redundancy.  The editor I use everyday can do
this for a wide range of programming languages, and matches
brackets/braces automatically too.

(All my personal opinions)

__Mark
[ markt@harlequin.co.uk | http://www.harlequin.co.uk/ | +44 1223 873829   ]
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