Prolog实现Wordle游戏：循环校验有效词长与随机选词问题

Let's tackle your two Wordle implementation issues in Prolog one by one, with clear fixes and explanations:

1. Fixing the Loop for Valid Word Length Check #

Your original check_length predicate has two key issues that break the loop logic:

• You're calling read(WordLength) again inside check_length, even though you already read the input in the play predicate—this causes unexpected duplicate input prompts.
• Using available_length(WordLength) = true is incorrect in Prolog: predicates succeed or fail natively; you don't need to compare them to true.

Additionally, your current available_length doesn't account for the selected category (it checks all categories), which would lead to invalid lengths being accepted if they exist in another category. Let's fix all of this:

Step 1: Update the Length Validation to Respect the Category #

First, redefine available_length to take the selected category as a parameter, so it only checks words in that category:

% Check if there exists a word of length Len in the given Category
available_length(Category, Len) :-
    word(W, Category),
    atom_chars(W, Chars),
    length(Chars, Len).

Step 2: Rewrite the Loop Predicate #

Modify check_length to accept the category and initial length as parameters. It will either succeed immediately (if valid) or prompt for a new input and recurse:

% Case 1: The entered length is valid—success
check_length(Category, WordLength) :-
    available_length(Category, WordLength), !. % Cut avoids unnecessary backtracking

% Case 2: Invalid length—prompt and recurse
check_length(Category, _) :-
    write('There are no words with this length in the chosen category.'),
    nl, write('Choose a length: '), nl,
    read(NewWordLength),
    check_length(Category, NewWordLength).

Step 3: Update the play Predicate #

Pass the selected category and initial length to check_length:

play:- 
    write('The available categories are: animals, greetings, fruits, collections'),
    nl, write('Choose a category: '), nl,
    read(Category), nl,
    write('Choose a length: '), nl,
    read(WordLength),
    check_length(Category, WordLength),
    Guesses is WordLength + 1,
    write('Game started. You have '), write(Guesses), write(' guesses.'),
    % Add random word selection here (see next section)
    random_word(Category, TargetWord),
    nl, write('(For testing: Target word is '), write(TargetWord), write(')').

2. Implementing Random Word Selection #

To pick a random word from the selected category, we'll first collect all words in that category into a list, then use Prolog's random library to select a member. This works in SWI-Prolog (the most common implementation):

Step 1: Import the Random Library #

Add this at the top of your file to access random utilities:

:- use_module(library(random)).

Step 2: Collect Words by Category #

Write a predicate to gather all unique words in the target category:

% Get a sorted list of all words in the given Category (sorted to avoid duplicates)
category_words(Category, Words) :-
    findall(W, word(W, Category), RawWords),
    sort(RawWords, Words).

Step 3: Randomly Select a Word #

Create a predicate that uses random_member/2 to pick a random word from the category list:

% Select a random word from the given Category
random_word(Category, TargetWord) :-
    category_words(Category, Words),
    random_member(TargetWord, Words).

Now when you run play, after validating the length, it will select a random target word from the chosen category—perfect for Wordle!

内容的提问来源于stack exchange，提问作者User2000