逻辑编程模型

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
fun {Soft} 
    % choice代表返回值要么是beige, 要么是coral
    choice beige 
        [] coral
    end
end

fun {Hard}
    % 同理
    choice mauve
        [] ochre
    end
end

proc {Contrast C1 C2}
    % 代表C1, C2的可选范围
    choice C1 = {Soft} C2 = {Hard}
       []  C1 = {Hard} C2 = {Soft}
    end
end

fun {Suit}
    Shirt Pants Socks
in
    % 定义了搜索空间
    {Contrast Shirt Pants}
    {Contrast Pants Socks}
    % 这里使用fail, 显式对搜索进行剪枝
    if Shirt == Socks then fail end
    suit(Shirt Pants Socks)
end

% 调用SolveAll进行求解
{Browse {SolveAll Suit}}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
-- 准备数据
CREATE TABLE colors (
    color_name VARCHAR(50) PRIMARY KEY,
    color_category VARCHAR(10) CHECK (color_category IN ('Hard', 'Soft'))
);

INSERT INTO colors (color_name, color_category) VALUES
('Mauve', 'Hard'),
('Ochre', 'Hard'),
('Beige', 'Soft'),
('Coral', 'Soft');

SELECT -- "solveAll"
    Shirt.color_name AS shirt_color,
    Pants.color_name AS pants_color,
    Socks.color_name AS socks_color,
    
FROM -- 指定搜索空间
    colors Shirt
CROSS JOIN 
    colors Pants
CROSS JOIN 
    colors Socks

WHERE -- 指定约束条件
    (
      (Shirt.color_category = "Soft" AND Pants.color_category = "Hard")
   OR
      (Shirt.color_category = "Hard" AND Pants.color_category = "Soft")
    )
    AND
    (
      (Pants.color_category = "Soft" AND Socks.color_category = "Hard")
      OR
      (Pants.color_category = "Hard" AND Socks.color_category = "Soft")
    )
    AND
    Shirt.color_name <> Socks.color_name

1
2
3
4
5
6
append([1, 2], [3, 4], [1, 2, 3, 4])        % True
append([1, 2], [5], L)                      % L == [1, 2, 5] 
append(L, [3, 4], [1, 2, 3, 4])             % L == [1, 2]
append([1, 2, 3], M, [1, 2, 3, 4])          % M = [4]
append([1, 2], [3], N)                      % N = [1, 2, 3]
append(P, Q, [1,2,3])                       % P = [] Q = [1,2,3]; P = [1] Q = [2, 3]; ...