10 research outputs found
The Best of Both Worlds:Linear Functional Programming without Compromise
We present a linear functional calculus with both the safety guarantees
expressible with linear types and the rich language of combinators and
composition provided by functional programming. Unlike previous combinations of
linear typing and functional programming, we compromise neither the linear side
(for example, our linear values are first-class citizens of the language) nor
the functional side (for example, we do not require duplicate definitions of
compositions for linear and unrestricted functions). To do so, we must
generalize abstraction and application to encompass both linear and
unrestricted functions. We capture the typing of the generalized constructs
with a novel use of qualified types. Our system maintains the metatheoretic
properties of the theory of qualified types, including principal types and
decidable type inference. Finally, we give a formal basis for our claims of
expressiveness, by showing that evaluation respects linearity, and that our
language is a conservative extension of existing functional calculi.Comment: Extended versio
Compositional Reasoning for Explicit Resource Management in Channel-Based Concurrency
We define a pi-calculus variant with a costed semantics where channels are
treated as resources that must explicitly be allocated before they are used and
can be deallocated when no longer required. We use a substructural type system
tracking permission transfer to construct coinductive proof techniques for
comparing behaviour and resource usage efficiency of concurrent processes. We
establish full abstraction results between our coinductive definitions and a
contextual behavioural preorder describing a notion of process efficiency
w.r.t. its management of resources. We also justify these definitions and
respective proof techniques through numerous examples and a case study
comparing two concurrent implementations of an extensible buffer.Comment: 51 pages, 7 figure
Modular, higher order cardinality analysis in theory and practice
Since the mid '80s, compiler writers for functional languages (especially lazy ones) have been writing papers about identifying and exploiting thunks and lambdas that are used only once. However, it has proved difficult to achieve both power and simplicity in practice. In this paper, we describe a new, modular analysis for a higher order language, which is both simple and effective. We prove the analysis sound with respect to a standard call-by-need semantics, and present measurements of its use in a full-scale, state-of-the-art optimising compiler. The analysis finds many single-entry thunks and one-shot lambdas and enables a number of program optimisations. This paper extends our preceding conference publication (Sergey et al. 2014 Proceedings of the 41st Annual ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages (POPL 2014). ACM, pp. 335–348) with proofs, expanded report on evaluation and a detailed examination of the factors causing the loss of precision in the analysis
Lazy Evaluation: From natural semantics to a machine-checked compiler transformation
In order to solve a long-standing problem with list fusion, a new compiler transformation, \u27Call Arity\u27 is developed and implemented in the Haskell compiler GHC. It is formally proven to not degrade program performance; the proof is machine-checked using the interactive theorem prover Isabelle. To that end, a formalization of Launchbury`s Natural Semantics for Lazy Evaluation is modelled in Isabelle, including a correctness and adequacy proof
Lazy Evaluation: From natural semantics to a machine-checked compiler transformation
In order to solve a long-standing problem with list fusion, a new compiler transformation, “Call Arity” is developed and implemented in the Haskell compiler GHC. It is formally proven to not degrade program performance; the proof is machine-checked using the interactive theorem prover Isabelle. To that end, a formalization of Launchbury’s Natural Semantics for Lazy Evaluation is modelled in Isabelle, including a correctness and adequacy proof