------------------------------------------------------------------------
-- Examples showing how Tree-sort can be used
------------------------------------------------------------------------

{-# OPTIONS --without-K --safe #-}

module Tree-sort.Examples where

open import Bag-equivalence
open import Equality.Propositional
import Nat equality-with-J as Nat
open import Prelude

-- Comparison functions for natural numbers.

_≤?_ :     Bool
m ≤? n with Nat.total m n
... | inj₁ m≤n = true
... | inj₂ n<m = false

import Tree-sort.Partial _≤?_ as P
open import Tree-sort.Full Nat._≤_ Nat.total as F using (cons; nil)

-- The sort functions return ordered lists.

orderedP : P.tree-sort (3  1  2  [])  1  2  3  []
orderedP = refl

orderedF : F.tree-sort (3  1  2  []) 
           cons 1 (cons 2 (cons 3 (nil _) _) _) _
orderedF = refl

-- The sort functions return lists which are bag equivalent to the
-- input. This property can be used to establish bag equivalences
-- between concrete lists.

a-bag-equivalenceP : 1  2  3  [] ≈-bag 3  1  2  []
a-bag-equivalenceP = P.tree-sort-permutes (3  1  2  [])

a-bag-equivalenceF : 1  2  3  [] ≈-bag 3  1  2  []
a-bag-equivalenceF = F.tree-sort-permutes (3  1  2  [])