[Haskell-cafe] Re: What *is* a DSL?

[Ben Franksen]

minh thu wrote:
> 2009/10/7 Günther Schmidt <gue.schmidt at web.de>:
>>> I've informally argued that a true DSL -- separate from a good API --
>>> should have semantic characteristics of a language: binding forms,
>>> control structures, abstraction, composition. Some have type systems.
>>>
>>
>> That is one requirement that confuses me, abstraction.
>>
>> I thought of DSLs as "special purpose" languages, ie. you give your DSL
>> everything it needs for that purpose.
>>
>> Why would it also need the ability to express even further abstractions,
>> it is supposed to *be* the abstraction.
>
> Programming abstractions at the DSL level, not to further abstract
> what the DSL covers.
> 
> Functions, for instance, are typical abstraction means offered by
> programming languages. Even if your language is specific to some
> domain, being able to create your own functions, and not only rely on
> those provided by the DSL implementation, is important.
> 
> Imagine a (E)DSL for 3D programming (e.g. shading language): the
> language is designed to fit well the problem (e.g. in this case, 3D
> linear algebra, color operations, ...) but you'll agree it would be a
> shame to not be able to provide your own functions.

But isn't one of the advantages of an _E_DSL that we can use the host
language (Haskell) as a meta or macro language for the DSL? I would think
that this greatly reduces the need to provide abstraction
facilities /inside/ the DSL. In fact most existing (and often cited
examples of) EDSLs in Haskell do not provide abstraction.

Cheers
Ben