README.md

In dirkschumacher/notail: Tail-call Optimization On The Byte-Code Level

notail

The goal of notail is to experiment with tail-call elimination on the byte-code level. It is purely for fun and educational purposes only and is the result of an evening hack.

It also uses internal R API functions, so it will never fully pass R CMD check.

Installation

You can install the development version of notail like so:

remotes::install_github("dirkschumacher/notail")

tailcall_eliminate

tailcall_eliminate takes a function. If that functions has a Recall call as the last operation, it will attempt to replace the recursion by a GOTO statement in the byte-code representation. Beware, this can have unintended effects, especially if the calls have side-effects.

Example

library(notail)
sum_n <- function(n, accumulator = 0) {
  if (n == 0) {
    return(accumulator)
  }
  Recall(n - 1, accumulator + n)
}
sum_n_2 <- tailcall_eliminate(sum_n)
try(sum_n(1000))
#> Error : evaluation nested too deeply: infinite recursion / options(expressions=)?
sum_n_2(1000)
#> [1] 500500
sum(1:1000)
#> [1] 500500

dirkschumacher/notail documentation built on Dec. 20, 2021, 12:03 a.m.