Re: Programming language specification languages

Nick Maclaren <nmm1@cus.cam.ac.uk> wrote:
> What I want is something enough beyond BNF that I can define
> type-consistency, scoping, aliasing and value-constraint rules. The
> really fancy stuff can be said in English.


Take a look at two-level grammars (van Wijngaarden). It's a sort of
"grammars with attributes"; you stuff the types (and scoping
information etc.) into the attributes.


I'm not sure whether van Wijngaarden-style grammars are the best way
to do this today, or even when I first read about them. However, I
once saw a Pascal-style language defined with it, and I found the
grammar extremely readable even though I had no knowledge of these
grammars at the time. (Actually I don't know much about them today; in
fact I think somebody mentioned that progress has been made on the
field since the early 80ies.)


Two-level grammars are on the "context-sensitive" tier of the Chomsky
hierarchy.


Regards,
Joachim

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