Beautifying Haskell programs (was: Re: pretty newby )

[Keith Wansbrough]

John Huges wrote:

> On Wed, 24 Sep 2003, Luc Taesch wrote:
> 
> > alos, Im surprised that this bland issue has not already been solved (PP
> > lib paper looks dated 96). no offence intended, but aas im newbie, i
[..]
> 
> As the author of the 96 paper (wasn't it 95?), let me defend it a bit, or
> at least explain what it offers, and what it does not.

I think the reason it "looks dated" is that it pretty much solved the
problem it was addressing.  For pretty-printing data structures, the
solution given in that paper does a rather good job, is configurable
in the ways you might want to configure it, and is fairly easy to use
and understand.  No one has needed to invent a new way of doing it
since.


Regarding beautifying Haskell programs: as John says, it's not
straightforward.  But I think the reason that there isn't such a thing
is that most people don't need it.  We mostly use editors that allow
us to get the indentation right, automatically, as we type the source
in, and we take care to preserve it as we edit, because it makes the
code easier to understand.

(note that there *are* tools for producing beautified documentation:
Haddock lists exports, type definitions, type signatures, and argument
and function documentation in HTML format, but it doesn't deal with
actual code).

And your other point, Luc, about generating type signatures
automatically, shows up something about your approach to debugging
code.  You should always put the type signatures in as you go -
preferably, before you write the function!  This is not just good
design practice and good documentation, it helps you debug the
function.  With type signatures, the compiler can see what you
intended to write, and verify that what you did write matches it.
Without type signatures, all it can see is that two things don't match
- it has no idea what you meant to type.  Try it: try putting in type
signatures, and see how much better the compiler's error messages
become.

Hope this helps..

--KW 8-)