Expose setting recursion limit in the API.
[hope.git] / src / hope_option.erl
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1-module(hope_option).
2
4af0774b 3-behavior(hope_monad).
2a40de4f 4
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5-export_type(
6 [ t/1
7 ]).
e492ea13 8
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9-export(
10 [ put/2
11 , get/2
4af0774b 12 , return/1
3b156801 13 , map/2
27a4f25f 14 , iter/2
4af0774b 15 , pipe/2
2497062c 16 , of_result/1
3b156801 17 ]).
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18
19
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20-type t(A) ::
21 none
22 | {some, A}
23 .
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24
25
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26-spec put(A, fun((A) -> boolean())) ->
27 t(A).
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28put(X, F) ->
29 case F(X)
30 of true -> {some, X}
31 ; false -> none
32 end.
33
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34-spec get(t(A), Default :: A) ->
35 A.
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36get({some, X}, _) -> X;
37get(none , Y) -> Y.
38
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39-spec return(A) ->
40 {some, A}.
41return(X) ->
42 {some, X}.
43
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44-spec map(t(A), fun((A) -> (B))) ->
45 t(B).
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46map({some, X}, F) -> {some, F(X)};
47map(none , _) -> none.
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48
49-spec iter(t(A), fun((A) -> (ok))) ->
50 ok.
51iter({some, X}, F) -> ok = F(X);
52iter(none , _) -> ok.
2497062c 53
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54-spec pipe([fun((A) -> t(B))], A) ->
55 t(B).
56pipe([], X) ->
57 return(X);
58pipe([F|Fs], X) ->
59 case F(X)
60 of none -> none
61 ; {some, Y} -> pipe(Fs, Y)
62 end.
63
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64-spec of_result(hope_result:t(A, _B)) ->
65 t(A).
66of_result({ok, X}) -> {some, X};
67of_result({error, _}) -> none.
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