Difference between revisions of "Embedded domain specific language"

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'''Embedded Domain Specific Language''' means that you embed a [http://en.wikipedia.org/wiki/Domain_specific_language Domain specific language] in a language like Haskell.
  
'''Embedded Domain Specific Language''' means that you embed a [http://en.wikipedia.org/wiki/Domain_specific_language Domain specific language] in a language like Haskell.
 
E.g. using the [http://cryp.to/funcmp/ Functional MetaPost library] you can write Haskell expressions, which are then translated to MetaPost, MetaPost is run on the generated code and the result of MetaPost can be post-processed in Haskell.
  
E.g. using the [http://cryp.to/funcmp/ Functional MetaPost library] you can write Haskell expressions, which are then translated to MetaPost, MetaPost is run on the generated code and the result of MetaPost can be post-processed in Haskell.
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== Degree of embedding ==
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There are two major degrees of embedding:
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* Shallow embedding: All Haskell operations immediately translate to the target language. E.g. the Haskell expression <hask>a+b</hask> is translated to a <hask>String</hask> like <hask>"a + b"</hask> containing that target language expression.
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* Deep embedding: Haskell operations only build an interim Haskell data structure that reflects the expression tree. E.g. the Haskell expression <hask>a+b</hask> is translated to the Haskell data structure <hask>Add (Var "a") (Var "b")</hask>. This structure allows transformations like optimizations before translating to the target language.
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== Discussion of common problems ==
  
== Discussion of common problems ==
   
 
[[Sharing]] and [http://en.wikipedia.org/wiki/Recursion recursion] are common problems when implementing DSLs.
  
[[Sharing]] and [http://en.wikipedia.org/wiki/Recursion recursion] are common problems when implementing DSLs.
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Often some kind of [[observable sharing]] is requested.
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Often some kind of [[observable sharing]] is requested
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that requires a deep embedding.
   
 
* Oleg in Haskell-Cafe about [http://www.haskell.org/pipermail/haskell-cafe/2008-February/039639.html Designing DSL with explicit sharing (was: I love purity, but it's killing me)]
  
* Oleg in Haskell-Cafe about [http://www.haskell.org/pipermail/haskell-cafe/2008-February/039639.html Designing DSL with explicit sharing (was: I love purity, but it's killing me)]
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* Koen Classen: [http://www.cs.chalmers.se/~koen/pubs/entry-asian99-lava.html Observable Sharing for Functional Circuit Description]
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* Koen Classen: [http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.31.4053 Observable Sharing for Functional Circuit Description]
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* Andy Gill: [http://www.ittc.ku.edu/~andygill/paper.php?label=DSLExtract09 Type-Safe Observable Sharing]
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* Andy Gill: [http://www.ittc.ku.edu/~andygill/papers/reifyGraph.pdf Type-Safe Observable Sharing]
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* Tom Lokhorst [http://tom.lokhorst.eu/2010/02/awesomeprelude-presentation-video AwesomePrelude presentation (video)]
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* Leandro Lisboa Penz [http://lpenz.github.com/articles/hedsl-sharedexpenses/ Haskell eDSL Tutorial - Shared expenses]
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* Bruno Oliveira and William Cook: [http://www.cs.utexas.edu/~wcook/Drafts/2012/graphs.pdf Functional Programming with Structured Graphs]
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== Examples of Domain Specific Languages ==
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* [http://hackage.haskell.org/package/funcmp Functional MetaPost] is a Haskell frontend to the MetaPost language by John Hobby. Users write their graphics as Haskell programs, which then emit MetaPost code that can be compiled into encapsulated PostScript files and smoothly included into e.g. LaTeX.
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* [http://hackage.haskell.org/package/orc orc]: Orchestration-style coordination EDSL
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* [http://hackage.haskell.org/package/diagrams-cairo The diagrams-cairo package]. A full-featured backend for rendering diagrams using the cairo rendering engine. To get started, see Diagrams.Backend.Cairo.CmdLine.
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* [http://hackage.haskell.org/package/Workflow Workflow]: library for transparent execution of interruptible computations
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* [http://www.yesodweb.com/book/templates#file253-synopsis Hamlet, Julius, Cassius and Lucius] are languages embedded in the [http://www.yesodweb.com/ Yesod framework]
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== More to read/view ==
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* [http://skillsmatter.com/podcast/scala/haskell-for-embedded-domain-specific-languages Haskell for embedded domain-specific languages] (podcast)
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* [[Research papers/Domain specific languages]]
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* [http://donsbot.wordpress.com/2007/03/10/practical-haskell-shell-scripting-with-error-handling-and-privilege-separation/ Practical Haskell: shell scripting with error handling and privilege separation] (blog article)
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[[Category:Glossary]]
  
[[Category:Glossary]]

Revision as of 14:50, 29 November 2012

Embedded Domain Specific Language means that you embed a Domain specific language in a language like Haskell. E.g. using the Functional MetaPost library you can write Haskell expressions, which are then translated to MetaPost, MetaPost is run on the generated code and the result of MetaPost can be post-processed in Haskell.


Degree of embedding

There are two major degrees of embedding:

  • Shallow embedding: All Haskell operations immediately translate to the target language. E.g. the Haskell expression a+b is translated to a String like "a + b" containing that target language expression.
  • Deep embedding: Haskell operations only build an interim Haskell data structure that reflects the expression tree. E.g. the Haskell expression a+b is translated to the Haskell data structure Add (Var "a") (Var "b"). This structure allows transformations like optimizations before translating to the target language.


Discussion of common problems

Sharing and recursion are common problems when implementing DSLs. Often some kind of observable sharing is requested that requires a deep embedding.

Examples of Domain Specific Languages

  • Functional MetaPost is a Haskell frontend to the MetaPost language by John Hobby. Users write their graphics as Haskell programs, which then emit MetaPost code that can be compiled into encapsulated PostScript files and smoothly included into e.g. LaTeX.
  • orc: Orchestration-style coordination EDSL
  • The diagrams-cairo package. A full-featured backend for rendering diagrams using the cairo rendering engine. To get started, see Diagrams.Backend.Cairo.CmdLine.
  • Workflow: library for transparent execution of interruptible computations

More to read/view

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