First Class Patterns?

Tullsen, Mark

doi:10.1007/3-540-46584-7_1

Cited by 24 publications

(25 citation statements)

References 6 publications

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“…This corresponds to the approaches used by Tullsen [Tullsen 2000] This setting also makes the rules (↿↾ ) and (⊘ ⊲ c → ⊘) sound (proofs are in Appendix D.4), which proves that PMC ⊘ as defined in [Kahl 2004] appropriately implements the semantics of Haskell.…”

Section: Haskellmentioning

confidence: 57%

“…Using a monad, most typically Maybe, for the semantics of pattern matching in Haskell-like languages has been proposed previously [Tullsen 2000 Since PMC offers a finer-grained, more systematic separation of pattern matching aspects from other expression evaluation aspects, choosing to interpret the two syntactic categories with separate monads is an obvious choice -the alternative of using a monad transformer deserves further exploration.…”

Section: Discussionmentioning

confidence: 99%

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Bimonadic Semantics for Basic Pattern Matching Calculi

Kahl

Carette

2006

Lecture Notes in Computer Science

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The pattern matching calculi introduced by the first author are a refinement of the λ-calculus that integrates mechanisms appropriate for fine-grained modelling of non-strict pattern matching.While related work in the literature only uses a single monad, typically Maybe, for matchings, we present an axiomatic approach to semantics of these pattern matching calculi using two monads, one for expressions and one for matchings.Although these two monads only need to be relatively lightly coupled, this semantics implies soundness of all core PMC rules, and is a useful tool for exploration of the design space for pattern matching calculi.Using lifting and Maybe monads, we obtain standard Haskell semantics, and by adding another level of Maybe to both, we obtain a denotational semantics of the "matching failure as exceptions" approach of Erwig and Peyton Jones. Using list-like monads opens up interesting extensions in the direction of functional-logic programming.A short version of this report appears as [Kahl, Carette + 2006].

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Section: Haskellmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 99%

Bimonadic Semantics for Basic Pattern Matching Calculi

Kahl

Carette

2006

Lecture Notes in Computer Science

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“…In spite of this disadvantage, we consider our pattern matching protocol, shown in Figure 2, significantly more straightforward than Newspeak's quadruple dispatch, shown in Figure 4. The idea of reifying patterns (rather than cases) as first class partial functions, and then building larger scale structures (e.g., case statements, clausal function definitions) out of pattern combinators goes back at least as far as Tullsen's first-class patterns proposal for Haskell [26]. Tullssen represents patterns as reified partial functions, and pattern combinators are thus function combinators.…”

Section: Discussion and Related Workmentioning

confidence: 99%

Patterns as objects in grace

Homer

Noble

Bruce

et al. 2012

Proceedings of the 8th Symposium on Dynamic Languages

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Object orientation and pattern matching are often seen as conflicting approaches to program design. Object oriented programs place type-dependent behaviour inside objects and invoke it via dynamic dispatch, while pattern matching programs place type-dependent behaviour outside data structures and invoke it via multiway conditionals (case statements). Grace is a new, dynamic, object-oriented language designed to support teaching: to this end, Grace needs to support both styles. In this paper we explain how this conflict can be resolved gracefully: by modelling patterns and cases as partial functions, reifying those functions as first-class objects, and then building up complex patterns from simpler ones using pattern combinators. We describe our design for pattern matching in Grace, and its implementation as an object-oriented framework.

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“…The next step will be an investigation of theory and denotational semantics of both calculi: For PMC , the most natural approach will be essentially the Maybe semantics of pattern matching as proposed in [21,9]. For PMC , the semantic domain for expressions needs to include an alternative for failure, too, to represent the semantics of empty expressions .…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, Tullsen includes a primitive "failure combinator" that never succeeds among his "First Class Patterns" combinators extending Haskell [21]. He uses a purely semantic approach, with functions into a Maybe type or, more generally, into a MonadPlus as "patterns".…”

Section: Related Workmentioning

confidence: 99%

Basic Pattern Matching Calculi: a Fresh View on Matching Failure

Kahl

2004

Functional and Logic Programming

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Abstract. We propose pattern matching calculi as a refinement of λ-calculus that integrates mechanisms appropriate for fine-grained modelling of non-strict pattern matching. Compared with the functional rewriting strategy usually employed to define the operational semantics of pattern matching in non-strict functional programming languages like Haskell or Clean, our pattern matching calculi achieve the same effects using simpler and more local rules. The main device is to embed into expressions the separate syntactic category of matchings; the resulting language naturally encompasses pattern guards and Boolean guards as special cases. By allowing a confluent reduction system and a normalising strategy, these pattern matching calculi provide a new basis for operational semantics of non-strict programming languages and also for implementations.

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First Class Patterns?

Cited by 24 publications

References 6 publications

Bimonadic Semantics for Basic Pattern Matching Calculi

Bimonadic Semantics for Basic Pattern Matching Calculi

Patterns as objects in grace

Basic Pattern Matching Calculi: a Fresh View on Matching Failure

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