The Cost of Skeletal Call-by-Need, Smoothly
Abstract
Skeletal call-by-need is an optimization of call-by-need evaluation also known as "fully lazy sharing": when the duplication of a value has to take place, it is first split into "skeleton", which is then duplicated, and "flesh" which is instead kept shared. Here, we provide two cost analyses of skeletal call-by-need. Firstly, we provide a family of terms showing that skeletal call-by-need can be asymptotically exponentially faster than call-by-need in both time and space; it is the first such evidence, to our knowledge. Secondly, we prove that skeletal call-by-need can be implemented efficiently, that is, with bi-linear overhead. This result is obtained by providing a new smooth presentation of ideas by Shivers and Wand for the reconstruction of skeletons, which is then smoothly plugged into the study of an abstract machine following the distillation technique by Accattoli et al.
Keywords
Cite
@article{arxiv.2505.09242,
title = {The Cost of Skeletal Call-by-Need, Smoothly},
author = {Beniamino Accattoli and Francesco Magliocca and Loïc Peyrot and Claudio Sacerdoti Coen},
journal= {arXiv preprint arXiv:2505.09242},
year = {2025}
}
Comments
Version with proof appendix of the FSCD 2025 paper with the same title