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6731749b SK |
1 | -module(hope_result). |
2 | ||
b69220d7 | 3 | -behavior(hope_gen_monad). |
2a40de4f | 4 | |
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5 | -export_type( |
6 | [ t/2 | |
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7 | , exn_class/0 |
8 | , exn_value/1 | |
3b156801 | 9 | ]). |
6731749b | 10 | |
3b156801 | 11 | -export( |
4af0774b SK |
12 | [ return/1 |
13 | , map/2 | |
a80ca0b2 SK |
14 | , map_error/2 |
15 | , tag_error/2 | |
4af0774b | 16 | , pipe/2 |
8fc25ea1 | 17 | , lift_exn/1 |
b79afea0 | 18 | , lift_exn/2 |
64617423 | 19 | , lift_map_exn/3 |
3b156801 | 20 | ]). |
6731749b | 21 | |
64617423 SK |
22 | -type exn_class() :: |
23 | error | |
24 | | exit | |
25 | | throw | |
26 | . | |
27 | ||
28 | -type exn_value(A) :: | |
29 | {exn_class(), A}. | |
6731749b | 30 | |
3b156801 SK |
31 | -type t(A, B) :: |
32 | {ok, A} | |
33 | | {error, B} | |
34 | . | |
6731749b SK |
35 | |
36 | ||
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37 | -spec return(A) -> |
38 | {ok, A}. | |
39 | return(X) -> | |
40 | {ok, X}. | |
41 | ||
42 | -spec map(t(A, Error), fun((A) -> (B))) -> | |
43 | t(B, Error). | |
44 | map({ok, X}, F) -> | |
45 | {ok, F(X)}; | |
46 | map({error, _}=Error, _) -> | |
47 | Error. | |
48 | ||
a80ca0b2 SK |
49 | -spec map_error(t(A, B), fun((B) -> (C))) -> |
50 | t(A, C). | |
51 | map_error({ok, _}=Ok, _) -> | |
52 | Ok; | |
53 | map_error({error, Reason}, F) -> | |
54 | {error, F(Reason)}. | |
55 | ||
56 | -spec tag_error(t(A, Reason), Tag) -> | |
57 | t(A, {Tag, Reason}). | |
58 | tag_error({ok, _}=Ok, _) -> | |
59 | Ok; | |
60 | tag_error({error, Reason}, Tag) -> | |
61 | {error, {Tag, Reason}}. | |
62 | ||
ed9905af SK |
63 | -spec pipe([F], X) -> |
64 | t(Ok, Error) | |
65 | when X :: any() | |
66 | , Ok :: any() | |
67 | , Error :: any() | |
68 | , F :: fun((X) -> t(Ok, Error)) | |
69 | . | |
3efbdbc9 SK |
70 | pipe([], X) -> |
71 | {ok, X}; | |
6731749b SK |
72 | pipe([F|Fs], X) -> |
73 | case F(X) | |
74 | of {error, _}=E -> E | |
75 | ; {ok, Y} -> pipe(Fs, Y) | |
76 | end. | |
8fc25ea1 SK |
77 | |
78 | -spec lift_exn(F) -> G | |
64617423 SK |
79 | when F :: fun((A) -> B) |
80 | , G :: fun((A) -> t(B, exn_value(any()))) | |
8fc25ea1 SK |
81 | . |
82 | lift_exn(F) when is_function(F, 1) -> | |
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83 | ID = fun hope_fun:id/1, |
84 | lift_map_exn(F, ID, ID). | |
85 | ||
86 | -spec lift_exn(F, ErrorTag) -> G | |
87 | when F :: fun((A) -> B) | |
88 | , G :: fun((A) -> t(B, {ErrorTag, exn_value(any())})) | |
89 | . | |
90 | lift_exn(F, ErrorTag) when is_function(F, 1) -> | |
91 | ID = fun hope_fun:id/1, | |
92 | Tag = fun (Reason) -> {ErrorTag, Reason} end, | |
93 | lift_map_exn(F, ID, Tag). | |
b79afea0 | 94 | |
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95 | -spec lift_map_exn(F, MapOk, MapError) -> G |
96 | when F :: fun((A) -> B) | |
97 | , MapOk :: fun((B) -> C) | |
98 | , MapError :: fun((exn_value(any())) -> Error) | |
99 | , G :: fun((A) -> t(C, Error)) | |
b79afea0 | 100 | . |
64617423 | 101 | lift_map_exn(F, MapOk, MapError) when is_function(F, 1) -> |
b79afea0 | 102 | fun(X) -> |
64617423 SK |
103 | Result = |
104 | try | |
105 | {ok, F(X)} | |
106 | catch Class:Reason -> | |
107 | {error, {Class, Reason}} | |
108 | end, | |
109 | % Applying maps separately as to not unintentionally catch an exception | |
110 | % raised in a map. | |
111 | case Result | |
112 | of {ok , _}=Ok -> map (Ok , MapOk) | |
113 | ; {error, _}=Error -> map_error(Error, MapError) | |
b79afea0 SK |
114 | end |
115 | end. |