1,483 research outputs found
Bounded Refinement Types
We present a notion of bounded quantification for refinement types and show
how it expands the expressiveness of refinement typing by using it to develop
typed combinators for: (1) relational algebra and safe database access, (2)
Floyd-Hoare logic within a state transformer monad equipped with combinators
for branching and looping, and (3) using the above to implement a refined IO
monad that tracks capabilities and resource usage. This leap in expressiveness
comes via a translation to "ghost" functions, which lets us retain the
automated and decidable SMT based checking and inference that makes refinement
typing effective in practice.Comment: 14 pages, International Conference on Functional Programming, ICFP
201
A universal formula for the relativistic correction to the mutual friction coupling time-scale in neutron stars
Vortex-mediated mutual friction governs the coupling between the superfluid
and normal components in neutron star interiors. By, for example, comparing
precise timing observations of pulsar glitches with theoretical predictions it
is possible to constrain the physics in the interior of the star, but to do so
an accurate model of the mutual friction coupling in general relativity is
needed. We derive such a model directly from Carter's multifluid formalism, and
study the vortex structure and coupling time-scale between the components in a
relativistic star. We calculate how general relativity modifies the shape and
the density of the quantized vortices and show that, in the quasi-Schwarzschild
coordinates, they can be approximated as straight lines for realistic neutron
star configurations. Finally, we present a simple universal formula (given as a
function of the stellar compactness alone) for the relativistic correction to
the glitch rise-time, which is valid under the assumption that the superfluid
reservoir is in a thin shell in the crust or in the outer core. This universal
relation can be easily employed to correct, a posteriori, any Newtonian
estimate for the coupling time-scale, without any additional computational
expense.Comment: 20 pages, 7 figure
First Class Call Stacks: Exploring Head Reduction
Weak-head normalization is inconsistent with functional extensionality in the
call-by-name -calculus. We explore this problem from a new angle via
the conflict between extensionality and effects. Leveraging ideas from work on
the -calculus with control, we derive and justify alternative
operational semantics and a sequence of abstract machines for performing head
reduction. Head reduction avoids the problems with weak-head reduction and
extensionality, while our operational semantics and associated abstract
machines show us how to retain weak-head reduction's ease of implementation.Comment: In Proceedings WoC 2015, arXiv:1606.0583
The Value of Regional Annual Nitrogen Needs Information for Wheat Producers in Oklahoma
Crop producers are increasingly interested in reducing nitrogen use without sacrificing yield. Technology is available for precise application at the sub-field level, but adoption has been sluggish. This paper estimates the relative profitability of a field level annual predictor of mid-season N requirements and a regional predictor of the same.nitrogen seeds, nitrogen use efficiency, precision agriculture, wheat, Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,
Trapped phonons
We analyze the effect of restricted geometries on the contribution of
Nambu-Goldstone bosons (phonons) to the shear viscosity, , of a
superfluid. For illustrative purpose we examine a simplified system consisting
of a circular boundary of radius , confining a two-dimensional rarefied gas
of phonons. Considering the Maxwell-type conditions, we show that phonons that
are not in equilibrium with the boundary and that are not specularly reflected
exert a shear stress on the boundary. In this case it is possible to define an
effective (ballistic) shear viscosity coefficient , where is the density of phonons and is a
parameter which characterizes the type of scattering at the boundary. For an
optically trapped superfluid our results corroborate the findings of Refs.
\cite{Mannarelli:2012su, Mannarelli:2012eg}, which imply that at very low
temperature the shear viscosity correlates with the size of the optical trap
and decreases with decreasing temperature.Comment: 8 pages, 5 figures, talk given at the conference "Xth Quark
Confinement and the Hadron Spectrum", October 8-12, 2012, TUM Campus
Garching, Munich, German
Counterexamples to simulation in non-deterministic call-by-need lambda-calculi with letrec
This note shows that in non-deterministic extended lambda calculi with letrec, the tool of applicative (bi)simulation is in general not usable for contextual equivalence, by giving a counterexample adapted from data flow analysis. It also shown that there is a flaw in a lemma and a theorem concerning finite simulation in a conference paper by the first two authors
What Does Aspect-Oriented Programming Mean for Functional Programmers?
Aspect-Oriented Programming (AOP) aims at modularising crosscutting concerns that show up in software. The success of AOP has been almost viral and nearly all areas in Software Engineering and Programming Languages have become "infected" by the AOP bug in one way or another. Interestingly the functional programming community (and, in particular, the pure functional programming community) seems to be resistant to the pandemic. The goal of this paper is to debate the possible causes of the functional programming community's resistance and to raise awareness and interest by showcasing the benefits that could be gained from having a functional AOP language. At the same time, we identify the main challenges and explore the possible design-space
Temporal Stream Logic: Synthesis beyond the Bools
Reactive systems that operate in environments with complex data, such as
mobile apps or embedded controllers with many sensors, are difficult to
synthesize. Synthesis tools usually fail for such systems because the state
space resulting from the discretization of the data is too large. We introduce
TSL, a new temporal logic that separates control and data. We provide a
CEGAR-based synthesis approach for the construction of implementations that are
guaranteed to satisfy a TSL specification for all possible instantiations of
the data processing functions. TSL provides an attractive trade-off for
synthesis. On the one hand, synthesis from TSL, unlike synthesis from standard
temporal logics, is undecidable in general. On the other hand, however,
synthesis from TSL is scalable, because it is independent of the complexity of
the handled data. Among other benchmarks, we have successfully synthesized a
music player Android app and a controller for an autonomous vehicle in the Open
Race Car Simulator (TORCS.
Synthesizing Functional Reactive Programs
Functional Reactive Programming (FRP) is a paradigm that has simplified the
construction of reactive programs. There are many libraries that implement
incarnations of FRP, using abstractions such as Applicative, Monads, and
Arrows. However, finding a good control flow, that correctly manages state and
switches behaviors at the right times, still poses a major challenge to
developers. An attractive alternative is specifying the behavior instead of
programming it, as made possible by the recently developed logic: Temporal
Stream Logic (TSL). However, it has not been explored so far how Control Flow
Models (CFMs), as synthesized from TSL specifications, can be turned into
executable code that is compatible with libraries building on FRP. We bridge
this gap, by showing that CFMs are indeed a suitable formalism to be turned
into Applicative, Monadic, and Arrowized FRP. We demonstrate the effectiveness
of our translations on a real-world kitchen timer application, which we
translate to a desktop application using the Arrowized FRP library Yampa, a web
application using the Monadic threepenny-gui library, and to hardware using the
Applicative hardware description language ClaSH.Comment: arXiv admin note: text overlap with arXiv:1712.0024
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