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
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