peano: Peano numbers

[ bsd3, data, library, math ] [ Propose Tags ]

Lazy unary natural numbers.

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Versions [RSS]	0.1.0.0, 0.1.0.1, 0.1.0.2
Change log	CHANGELOG.md
Dependencies	base (>=4.9 && <5) [details]
License	BSD-3-Clause
Author	M Farkas-Dyck, Andreas Abel
Maintainer	Andreas Abel
Category	Data, Math
Source repo	head: git clone https://github.com/andreasabel/peano.hs
Uploaded	by AndreasAbel at 2023-10-23T09:30:25Z
Distributions	Arch:0.1.0.1, LTSHaskell:0.1.0.2, NixOS:0.1.0.2, Stackage:0.1.0.2
Reverse Dependencies	11 direct, 14 indirect [details]
Downloads	3650 total (111 in the last 30 days)
Rating	(no votes yet) [estimated by Bayesian average]
Your Rating	λ λ λ
Status	Docs available [build log] Last success reported on 2023-10-23 [all 1 reports]

This package provides natural numbers in unary notation

data Peano
  = Zero
  | Succ Peano

implementing Num, Ord etc.

One application is to check whether the length of a (potentially long) list is greater than a (small) number.

E.g., without optimization (-O 0),

genericLength (replicate (10 ^ 6) True) >= (5 :: Peano)

outperforms the same test for 5 :: Int by a factor of 10⁵, see benchmark:

  length
    Peano: OK
      450  ns ±  45 ns
    Int:   OK
      136  ms ± 4.1 ms