So, if I understand this: Parsec is a DSL, I'm going to venture it's a "Deep embedding" -- I don't understand the internals, but if I were to build something like Parsec, I would probably build up a "Parser" datastructure and then apply optimizations to it, then "run" it with another function. Am I on the right track here? /Joe On Oct 7, 2009, at 11:24 AM, Emil Axelsson wrote:
Hi,
A DSL is just a domain-specific language. It doesn't imply any specific implementation technique.
An *embedded* DSL is a library implemented in a more general language, which has been designed to give the "feeling" of a stand- alone language. Still nothing about implementation.
A *shallow embedding* of a DSL is when the "evaluation" is done immediately by the functions and combinators of the DSL. I don't think it's possible to draw a line between a combinator library and a shallowly embedded DSL.
A *deep embedding* is when interpretation is done on an intermediate data structure.
/ Emil
Günther Schmidt skrev:
Hi all, for people that have followed my posts on the DSL subject this question probably will seem strange, especially asking it now. I have read quite a lot lately on the subject, most of it written by the great old ones, (come on guys you know whom I mean :)). What I could gather from their papers was, that a DSL is basically something entirely abstract as such, ie. it allows you build and combine expressions in a language which is specific for your problem domain. Irregardless of further details on how to do that, and there are quite a few, the crux as such is that they are abstract of "meaning". The meaning depends how you *evaluate* the expression, which can be in more than merely one way, which is where, as far as I understand it, the true power lies. So, you might wonder, since I figured it out this far, why ask what a DSL is? Because out there I see quite a lot of stuff that is labeled as DSL, I mean for example packages on hackage, quite useuful ones too, where I don't see the split of assembling an expression tree from evaluating it, to me that seems more like combinator libraries. Thus: What is a DSL? Günther _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
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