Commit | Line | Data |
---|---|---|
e492ea13 SK |
1 | -module(hope_option). |
2 | ||
b69220d7 | 3 | -behavior(hope_gen_monad). |
2a40de4f | 4 | |
3b156801 SK |
5 | -export_type( |
6 | [ t/1 | |
7 | ]). | |
e492ea13 | 8 | |
3b156801 | 9 | -export( |
1c003d17 SK |
10 | % Generic monad interface |
11 | [ return/1 | |
3b156801 | 12 | , map/2 |
4af0774b | 13 | , pipe/2 |
1c003d17 SK |
14 | |
15 | % Specific to hope_option:t() | |
16 | , return/2 | |
17 | , put/2 | |
18 | , get/2 | |
19 | , iter/2 | |
2497062c | 20 | , of_result/1 |
f2e1fffc | 21 | , of_undefined/1 |
5fab324a | 22 | , to_undefined/1 |
352ddeb4 | 23 | , validate/2 |
3b156801 | 24 | ]). |
e492ea13 SK |
25 | |
26 | ||
3b156801 SK |
27 | -type t(A) :: |
28 | none | |
29 | | {some, A} | |
30 | . | |
e492ea13 SK |
31 | |
32 | ||
ed9905af SK |
33 | -spec put(A, fun((A) -> boolean())) -> |
34 | t(A). | |
e492ea13 | 35 | put(X, F) -> |
9a5e47fa | 36 | return(X, F). |
e492ea13 | 37 | |
ed9905af SK |
38 | -spec get(t(A), Default :: A) -> |
39 | A. | |
e492ea13 SK |
40 | get({some, X}, _) -> X; |
41 | get(none , Y) -> Y. | |
42 | ||
4af0774b SK |
43 | -spec return(A) -> |
44 | {some, A}. | |
45 | return(X) -> | |
46 | {some, X}. | |
47 | ||
9a5e47fa SK |
48 | -spec return(A, fun((A) -> boolean())) -> |
49 | t(A). | |
50 | return(X, Condition) -> | |
51 | case Condition(X) | |
52 | of true -> {some, X} | |
53 | ; false -> none | |
54 | end. | |
55 | ||
ed9905af SK |
56 | -spec map(t(A), fun((A) -> (B))) -> |
57 | t(B). | |
e492ea13 SK |
58 | map({some, X}, F) -> {some, F(X)}; |
59 | map(none , _) -> none. | |
27a4f25f | 60 | |
0ed4baeb | 61 | -spec iter(t(A), fun((A) -> (any()))) -> |
4744fed9 | 62 | {}. |
0ed4baeb SK |
63 | iter({some, X}, F) -> |
64 | _ = F(X), | |
4744fed9 | 65 | {}; |
0ed4baeb | 66 | iter(none, _) -> |
4744fed9 | 67 | {}. |
2497062c | 68 | |
4af0774b SK |
69 | -spec pipe([fun((A) -> t(B))], A) -> |
70 | t(B). | |
71 | pipe([], X) -> | |
72 | return(X); | |
73 | pipe([F|Fs], X) -> | |
74 | case F(X) | |
75 | of none -> none | |
76 | ; {some, Y} -> pipe(Fs, Y) | |
77 | end. | |
78 | ||
2497062c SK |
79 | -spec of_result(hope_result:t(A, _B)) -> |
80 | t(A). | |
81 | of_result({ok, X}) -> {some, X}; | |
82 | of_result({error, _}) -> none. | |
f2e1fffc SK |
83 | |
84 | -spec of_undefined(undefined | A) -> | |
85 | t(A). | |
86 | of_undefined(undefined) -> none; | |
87 | of_undefined(X) -> {some, X}. | |
352ddeb4 | 88 | |
5fab324a SK |
89 | -spec to_undefined(t(A)) -> |
90 | undefined | A. | |
91 | to_undefined(none) -> undefined; | |
92 | to_undefined({some, X}) -> X. | |
93 | ||
352ddeb4 SK |
94 | -spec validate(t(A), fun((A) -> boolean())) -> |
95 | t(A). | |
96 | validate(none, _) -> | |
97 | none; | |
98 | validate({some, X}=T, F) -> | |
99 | case F(X) | |
100 | of false -> none | |
101 | ; true -> T | |
102 | end. |