Add haskell-src as an official machine-readable component of the Haskell standard

Yitzchak Gale gale at
Wed Nov 17 17:20:34 EST 2010

Ben Millwood wrote:
> But if we make the official parser usable for AST manipulation, we
> have to rule on the design issues I raised above: whether to make
> efforts to stop invalid lambdas being constructed, how to name the
> types and constructors, etc.

No we don't. With regard to its inclusion as part of the
standard, we make only one guarantee - that it serves
to verify whether code is compliant to the standard.

For your convenience, the package maintainer will try
to make it useful for other things too, but in that respect
it is no different than any other package on Hackage.

> What purpose does it serve that a Haskell
> parser independent of the report does not?

Machine verification of Haskell 20nn standards compliance.

> We can't guarantee it's bug-free

We can't guarantee that the human-readable part of
the standard is bug-free, either. It always has had
bugs and it always will, like any standard. We do
the best we can.

Actually, there is the possibility of developing an
automated system to generate unit tests from the
standards document to verify the consistency of
the parser with the document. Those same unit tests
could then also be used by compiler writers to certify
the compliance of their Haskell 20nn mode and
do regression testing.

There are many intriguing possibilities.

> I suppose providing a reference parser at least ensures that any
> modification to Haskell syntax is implementable, and the issues in its
> implementation will have been considered

Yes that is one of the advantages of this approach.

> but in practice every
> alteration to the Haskell language from now on is going to be
> standardising extensions that already exist, so I don't really think
> this is a priority.

For you it may not be a priority. But for enterprise project
architects who are required to consider and document
every possible risk before agreeing to adopt Haskell,
it is a priority.


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