How to resolve the algorithm Burrows–Wheeler transform step by step in the BQN programming language

Published on 12 May 2024 09:40 PM
#Bqn

How to resolve the algorithm Burrows–Wheeler transform step by step in the BQN programming language

Table of Contents

Problem Statement

The Burrows–Wheeler transform (BWT, also called block-sorting compression) rearranges a character string into runs of similar characters. This is useful for compression, since it tends to be easy to compress a string that has runs of repeated characters by techniques such as move-to-front transform and run-length encoding. More importantly, the transformation is reversible, without needing to store any additional data. The BWT is thus a "free" method of improving the efficiency of text compression algorithms, costing only some extra computation.

Source: Burrows–Wheeler transform

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Burrows–Wheeler transform step by step in the BQN programming language

Source code in the bqn programming language

stx←@+2
BWT ← { # Burrows-Wheeler Transform and its inverse as an invertible function
  𝕊: "Input contained STX"!⊑stx¬∘∊𝕩 ⋄ (⍋↓𝕩) ⊏ stx∾𝕩;
  𝕊⁼: 1↓(⊑˜⍟(↕≠𝕩)⟜⊑ ⍋)⊸⊏ 𝕩
}


    BWT "banana"
"annb␂aa"
    BWT⁼ BWT "banana"
"banana"

    BWT "appellee"
"e␂elplepa"
    BWT⁼ BWT "appellee"
"appellee"

    BWT "dogwood"
"do␂oodwg"
    BWT⁼ BWT "dogwood"
"dogwood"

    BWT "TO BE OR NOT TO BE OR WANT TO BE OR NOT?"
"?OOORREEETTRTW   BBB  ATTT   NNOOONOO␂   "
    BWT⁼ BWT "TO BE OR NOT TO BE OR WANT TO BE OR NOT?"
"TO BE OR NOT TO BE OR WANT TO BE OR NOT?"

    BWT "SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES"
"STEXYDST.E.IXXIIXXSSMPPS.B..EE.␂.USFXDIIOIIIT"
    BWT⁼ BWT "SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES"
"SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES"

    BWT "␂abc"
Error: Input contained STX

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