Arc-Length Statistics: Goodness of Fit, Distributions and a Bayesian Test R package arcstat version 0.3.0 Inference from the arc length of statistical functions. Three tools share one pure-C back-end: a goodness-of-fit test based on the arc length of the probability plot, with an analytic saddlepoint null and sensitivity to local density structure that the empirical-distribution tests miss; two constructions that build a distribution from the arc length of its defining curve, the arc-length generator and the quantile arc-length family estimated by L-moments; and a Bayesian nonparametric arc-length goodness-of-fit test on the Dirichlet-process posterior. The same C sources back the 'Python' package 'arcstat'. Software Imports: stats Suggests: MASS, knitr, rmarkdown, testthat (>= 3.0.0) M. Theodor Loots <theo.loots@gmail.com> Comprehensive R Archive Network (CRAN) M. Theodor Loots [aut, cre] (ORCID: <https://orcid.org/0000-0001-7722-3913>) GPL-3 2026-09-14 application/tgz https://CRAN.R-project.org/package=arcstat doi:10.32614/CRAN.package.arcstat