How to resolve the algorithm Word frequency step by step in the Prolog programming language

Published on 12 May 2024 09:40 PM
#Prolog

How to resolve the algorithm Word frequency step by step in the Prolog programming language

Table of Contents

Problem Statement

Given a text file and an integer   n,   print/display the   n   most common words in the file   (and the number of their occurrences)   in decreasing frequency.

For the purposes of this task:

Show example output using Les Misérables from Project Gutenberg as the text file input and display the top   10   most used words.

This task was originally taken from programming pearls from Communications of the ACM June 1986 Volume 29 Number 6 where this problem is solved by Donald Knuth using literate programming and then critiqued by Doug McIlroy, demonstrating solving the problem in a 6 line Unix shell script (provided as an example below).

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Word frequency step by step in the Prolog programming language

Source code in the prolog programming language

print_top_words(File, N):-
    read_file_to_string(File, String, [encoding(utf8)]),
    re_split("\\w+", String, Words),
    lower_case(Words, Lower),
    sort(1, @=<, Lower, Sorted),
    merge_words(Sorted, Counted),
    sort(2, @>, Counted, Top_words),
    writef("Top %w words:\nRank\tCount\tWord\n", [N]),
    print_top_words(Top_words, N, 1).

lower_case([_], []):-!.
lower_case([_, Word|Words], [Lower - 1|Rest]):-
    string_lower(Word, Lower),
    lower_case(Words, Rest).

merge_words([], []):-!.
merge_words([Word - C1, Word - C2|Words], Result):-
    !,
    C is C1 + C2,
    merge_words([Word - C|Words], Result).
merge_words([W|Words], [W|Rest]):-
    merge_words(Words, Rest).

print_top_words([], _, _):-!.
print_top_words(_, 0, _):-!.
print_top_words([Word - Count|Rest], N, R):-
    writef("%w\t%w\t%w\n", [R, Count, Word]),
    N1 is N - 1,
    R1 is R + 1,
    print_top_words(Rest, N1, R1).

main:-
    print_top_words("135-0.txt", 10).

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