Implementing explicit and finding implicit sharing in embedded DSLs

Research output: Contribution to journalConference articlepeer-review

3 Citations (Scopus)


Aliasing, or sharing, is prominent in many domains, denoting that two differently-named objects are in fact identical: a change in one object (memory cell, circuit terminal, disk block) is instantly reflected in the other. Languages for modelling such domains should let the programmer explicitly define the sharing among objects or expressions. A DSL compiler may find other identical expressions and share them, implicitly. Such common subexpression elimination is crucial to the efficient implementation of DSLs. Sharing is tricky in embedded DSL, since host aliasing may correspond to copying of the underlying objects rather than their sharing. This tutorial summarizes discussions of implementing sharing in Haskell DSLs for automotive embedded systems and hardware description languages. The technique has since been used in a Haskell SAT solver and the DSL for music synthesis. We demonstrate the embedding in pure Haskell of a simple DSL with a language form for explicit sharing. The DSL also has implicit sharing, implemented via hash-consing. Explicit sharing greatly speeds up hash-consing. The seemingly imperative nature of hash-consing is hidden beneath a simple combinator language. The overall implementation remains pure functional and easy to reason about. I think all DSLs suffer from the same problems: sharing and recursion. I've used wrappers for CSound, SuperCollider, MetaPost, they all have these problems. Henning Thielemann [19].

Original languageEnglish
Pages (from-to)210-225
Number of pages16
JournalElectronic Proceedings in Theoretical Computer Science, EPTCS
Publication statusPublished - 2011 Sept 1
Event2nd IFIP Working Conference on Domain-Specific Languages, DSL 2011 - Bordeaux, France
Duration: 2011 Sept 62011 Sept 8


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