Added tests and docs for combinatorics.list_permutation function behaviour on duplicate elements

This commit is contained in:
Daniel 2023-11-19 22:40:59 +00:00
parent 788e142466
commit 52281ce431
2 changed files with 40 additions and 2 deletions

View file

@ -319,6 +319,18 @@ fn do_list_combination(arr: List(a), k: Int, prefix: List(a)) -> List(List(a)) {
///
/// Generate all permutations of a given list.
///
/// Repeated elements are treated as distinct for the
/// purpose of permutations, so two identical elements
/// for example will appear "both ways round". This
/// means lists with repeated elements return the same
/// number of permutations as ones without.
///
/// N.B. The output of this function is a list of size
/// factorial in the size of the input list. Caution is
/// advised on input lists longer than ~11 elements, which
/// may cause the VM to use unholy amounts of memory for
/// the output.
///
/// <details>
/// <summary>Example:</summary>
///
@ -338,6 +350,10 @@ fn do_list_combination(arr: List(a), k: Int, prefix: List(a)) -> List(List(a)) {
/// [2, 3, 1],
/// [3, 2, 1],
/// ]))
///
/// [1.0, 1.0]
/// |> combinatorics.list_permutation()
/// |> should.equal([[1.0, 1.0], [1.0, 1.0]])
/// }
/// </details>
///

View file

@ -1,5 +1,6 @@
import gleam_community/maths/combinatorics
import gleam/set
import gleam/list
import gleeunit
import gleeunit/should
@ -103,15 +104,22 @@ pub fn list_cartesian_product_test() {
}
pub fn list_permutation_test() {
// An empty lists returns an empty list
// An empty lists returns one (empty) permutation
[]
|> combinatorics.list_permutation()
|> should.equal([[]])
// Singleton returns one (singleton) permutation
// Also works regardless of type of list elements
["a"]
|> combinatorics.list_permutation()
|> should.equal([["a"]])
// Test with some arbitrary inputs
[1, 2]
|> combinatorics.list_permutation()
|> should.equal([[1, 2], [2, 1]])
|> set.from_list()
|> should.equal(set.from_list([[1, 2], [2, 1]]))
// Test with some arbitrary inputs
[1, 2, 3]
@ -125,6 +133,20 @@ pub fn list_permutation_test() {
[2, 3, 1],
[3, 2, 1],
]))
// Repeated elements are treated as distinct for the
// purpose of permutations, so two identical elements
// will appear "both ways round"
[1.0, 1.0]
|> combinatorics.list_permutation()
|> should.equal([[1.0, 1.0], [1.0, 1.0]])
// This means lists with repeated elements return the
// same number of permutations as ones without
["l", "e", "t", "t", "e", "r", "s"]
|> combinatorics.list_permutation()
|> list.length()
|> should.equal(5040)
}
pub fn list_combination_test() {