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48290 results in Computer Science

Page 327 of 2415

  • ANF preserves dependent types up to extensional equality

  • PAULETTE KORONKEVICH, RAMON RAKOW, AMAL AHMED, WILLIAM J. BOWMAN
  • Journal:
    Journal of Functional Programming / Volume 32 / 2022
    Published online by Cambridge University Press:
    16 September 2022, e12
    • Article
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  • Many programmers use dependently typed languages such as Coq to machine-verify high-assurance software. However, existing compilers for these languages provide no guarantees after compiling, nor when linking after compilation. Type-preserving compilers preserve guarantees encoded in types and then use type checking to verify compiled code and ensure safe linking with external code. Unfortunately, standard compiler passes do not preserve the dependent typing of commonly used (intensional) type theories. This is because assumptions valid in simpler type systems no longer hold, and intensional dependent type systems are highly sensitive to syntactic changes, including compilation. We develop an A-normal form (ANF) translation with join-point optimization—a standard translation for making control flow explicit in functional languages—from the Extended Calculus of Constructions (ECC) with dependent elimination of booleans and natural numbers (a representative subset of Coq). Our dependently typed target language has equality reflection, allowing the type system to encode semantic equality of terms. This is key to proving type preservation and correctness of separate compilation for this translation. This is the first ANF translation for dependent types. Unlike related translations, it supports the universe hierarchy, and does not rely on parametricity or impredicativity.

The Flexibility Paradox
  • Why Flexible Working Leads to (Self-)Exploitation
  • Heejung Chung
  • Published by:
    Bristol University Press
    Published online:
    15 September 2022
    Print publication:
    04 March 2022
  • Throughout the COVID-19 pandemic, flexible working has become the norm for many workers. This volume offers an original examination of flexible working using data from 30 European countries and drawing on studies conducted in Australia, the US and India. Rather than providing a better work-life balance, the book reveals how flexible working can lead to exploitation, which manifests differently for women and men, such as more care responsibilities or increased working hours.

  • 10 - Working with Predicate Logic Proofs

  • from Part II - Predicate Logic
  • Yannai A. Gonczarowski, Harvard University, Massachusetts, Noam Nisan, Hebrew University of Jerusalem
  • Book:
    Mathematical Logic through Python
    Published online:
    25 August 2022
    Print publication:
    15 September 2022, pp 178-210

  • Summary

    In this chapter we fix a specific axiomatic system and provide several examples of its formal use. These include logical inferences such as syllogisms, proofs of mathematical theorems in structures such as groups and fields, and foundations of mathematics, specifically Peano Arithmetic and Set Theory.

  • Trajectory optimization of the redundant manipulator with local variable period under multi-machine coordination

  • Luchuan Yu, Shunqing Zhou, Shenquan Huang
  • Journal:
    Robotica / Volume 41 / Issue 1 / January 2023
    Published online by Cambridge University Press:
    15 September 2022, pp. 292-305

  • The coordinated motion between the press and the feeding mechanism directly determines the production efficiency of the high-speed stamping line. In order to generate the high-performance trajectory of the feeding mechanism, this paper investigates the optimization of the trajectory with the local variable period. Based on the quintic B-spline curve and normal distribution, the smooth interpolation method of variable-time interval is proposed to generate the collision-free and energy-jerk-minimal trajectory with variable-time intervals. The advantage of the proposed method is that it can make the feeding mechanism transition smoothly between districts of variable-time and fixed-time intervals. It is beneficial to avoid re-performing the entire process of trajectory planning. ADAMS and actual experiments are used to validate the effectiveness of the proposed method. Results show that the proposed method can maintain the high performance of the initial trajectory, and there is no sharp point in the displacement-time and velocity-time curves. The investigation provides a new direction for the direct generation of local variable-period trajectories in the multi-machine coordination of the stamping line.

Page 327 of 2415