Commit | Line | Data |
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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 |
3b156801 | 22 | ]). |
e492ea13 SK |
23 | |
24 | ||
3b156801 SK |
25 | -type t(A) :: |
26 | none | |
27 | | {some, A} | |
28 | . | |
e492ea13 SK |
29 | |
30 | ||
ed9905af SK |
31 | -spec put(A, fun((A) -> boolean())) -> |
32 | t(A). | |
e492ea13 | 33 | put(X, F) -> |
9a5e47fa | 34 | return(X, F). |
e492ea13 | 35 | |
ed9905af SK |
36 | -spec get(t(A), Default :: A) -> |
37 | A. | |
e492ea13 SK |
38 | get({some, X}, _) -> X; |
39 | get(none , Y) -> Y. | |
40 | ||
4af0774b SK |
41 | -spec return(A) -> |
42 | {some, A}. | |
43 | return(X) -> | |
44 | {some, X}. | |
45 | ||
9a5e47fa SK |
46 | -spec return(A, fun((A) -> boolean())) -> |
47 | t(A). | |
48 | return(X, Condition) -> | |
49 | case Condition(X) | |
50 | of true -> {some, X} | |
51 | ; false -> none | |
52 | end. | |
53 | ||
ed9905af SK |
54 | -spec map(t(A), fun((A) -> (B))) -> |
55 | t(B). | |
e492ea13 SK |
56 | map({some, X}, F) -> {some, F(X)}; |
57 | map(none , _) -> none. | |
27a4f25f SK |
58 | |
59 | -spec iter(t(A), fun((A) -> (ok))) -> | |
60 | ok. | |
61 | iter({some, X}, F) -> ok = F(X); | |
62 | iter(none , _) -> ok. | |
2497062c | 63 | |
4af0774b SK |
64 | -spec pipe([fun((A) -> t(B))], A) -> |
65 | t(B). | |
66 | pipe([], X) -> | |
67 | return(X); | |
68 | pipe([F|Fs], X) -> | |
69 | case F(X) | |
70 | of none -> none | |
71 | ; {some, Y} -> pipe(Fs, Y) | |
72 | end. | |
73 | ||
2497062c SK |
74 | -spec of_result(hope_result:t(A, _B)) -> |
75 | t(A). | |
76 | of_result({ok, X}) -> {some, X}; | |
77 | of_result({error, _}) -> none. | |
f2e1fffc SK |
78 | |
79 | -spec of_undefined(undefined | A) -> | |
80 | t(A). | |
81 | of_undefined(undefined) -> none; | |
82 | of_undefined(X) -> {some, X}. |