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a6244ba2 SK |
1 | -module(hope_list). |
2 | ||
3 | -export_type( | |
4 | [ t/1 | |
5 | ]). | |
6 | ||
7 | -export( | |
8 | [ unique_preserve_order/1 | |
ff793acf | 9 | , map/2 |
781f182f | 10 | , map/3 % Tunable recursion limit |
c66ddf80 | 11 | , map_rev/2 |
2a81fbac | 12 | , map_slow/2 |
a626cf31 | 13 | , first_match/2 |
a6244ba2 SK |
14 | ]). |
15 | ||
16 | ||
781f182f | 17 | -define(DEFAULT_RECURSION_LIMIT, 1000). |
ff793acf SK |
18 | |
19 | ||
a6244ba2 SK |
20 | -type t(A) :: |
21 | [A]. | |
22 | ||
23 | ||
ff793acf SK |
24 | %% @doc Tail-recursive equivalent of lists:map/2 |
25 | %% @end | |
26 | -spec map([A], fun((A) -> (B))) -> | |
27 | [B]. | |
28 | map(Xs, F) -> | |
781f182f | 29 | map(Xs, F, ?DEFAULT_RECURSION_LIMIT). |
ff793acf | 30 | |
781f182f | 31 | -spec map([A], fun((A) -> (B)), RecursionLimit :: non_neg_integer()) -> |
ff793acf | 32 | [B]. |
781f182f SK |
33 | map(Xs, F, RecursionLimit) -> |
34 | map(Xs, F, RecursionLimit, 0). | |
35 | ||
36 | map([], _, _, _) -> | |
ff793acf | 37 | []; |
781f182f | 38 | map([X1], F, _, _) -> |
ff793acf SK |
39 | Y1 = F(X1), |
40 | [Y1]; | |
781f182f | 41 | map([X1, X2], F, _, _) -> |
ff793acf SK |
42 | Y1 = F(X1), |
43 | Y2 = F(X2), | |
44 | [Y1, Y2]; | |
781f182f | 45 | map([X1, X2, X3], F, _, _) -> |
ff793acf SK |
46 | Y1 = F(X1), |
47 | Y2 = F(X2), | |
48 | Y3 = F(X3), | |
49 | [Y1, Y2, Y3]; | |
781f182f | 50 | map([X1, X2, X3, X4], F, _, _) -> |
ff793acf SK |
51 | Y1 = F(X1), |
52 | Y2 = F(X2), | |
53 | Y3 = F(X3), | |
54 | Y4 = F(X4), | |
55 | [Y1, Y2, Y3, Y4]; | |
781f182f | 56 | map([X1, X2, X3, X4, X5 | Xs], F, RecursionLimit, RecursionCount) -> |
ff793acf SK |
57 | Y1 = F(X1), |
58 | Y2 = F(X2), | |
59 | Y3 = F(X3), | |
60 | Y4 = F(X4), | |
61 | Y5 = F(X5), | |
62 | Ys = | |
781f182f | 63 | case RecursionCount > RecursionLimit |
ff793acf | 64 | of true -> map_slow(Xs, F) |
781f182f | 65 | ; false -> map (Xs, F, RecursionLimit, RecursionCount + 1) |
ff793acf SK |
66 | end, |
67 | [Y1, Y2, Y3, Y4, Y5 | Ys]. | |
68 | ||
69 | ||
2a81fbac SK |
70 | %% @doc lists:reverse(map_rev(L, F)) |
71 | %% @end | |
72 | -spec map_slow([A], fun((A) -> (B))) -> | |
73 | [B]. | |
74 | map_slow(Xs, F) -> | |
75 | lists:reverse(map_rev(Xs, F)). | |
76 | ||
77 | ||
5e20a667 SK |
78 | %% @doc Tail-recursive alternative to lists:map/2, which accumulates and |
79 | %% returns list in reverse order. | |
c66ddf80 SK |
80 | %% @end |
81 | -spec map_rev([A], fun((A) -> (B))) -> | |
82 | [B]. | |
83 | map_rev(Xs, F) -> | |
84 | map_rev_acc(Xs, F, []). | |
85 | ||
86 | -spec map_rev_acc([A], fun((A) -> (B)), [B]) -> | |
87 | [B]. | |
88 | map_rev_acc([], _, Ys) -> | |
89 | Ys; | |
90 | map_rev_acc([X|Xs], F, Ys) -> | |
91 | Y = F(X), | |
92 | map_rev_acc(Xs, F, [Y|Ys]). | |
93 | ||
94 | ||
a6244ba2 SK |
95 | -spec unique_preserve_order(t(A)) -> |
96 | t(A). | |
97 | unique_preserve_order(L) -> | |
17b5d686 | 98 | PrependIfNew = |
a6244ba2 SK |
99 | fun (X, Xs) -> |
100 | case lists:member(X, Xs) | |
17b5d686 SK |
101 | of true -> Xs |
102 | ; false -> [X | Xs] | |
a6244ba2 SK |
103 | end |
104 | end, | |
17b5d686 | 105 | lists:reverse(lists:foldl(PrependIfNew, [], L)). |
a626cf31 SK |
106 | |
107 | -spec first_match([{Tag, fun((A) -> boolean())}], A) -> | |
108 | hope_option:t(Tag). | |
109 | first_match([], _) -> | |
110 | none; | |
111 | first_match([{Tag, F} | Tests], X) -> | |
112 | case F(X) | |
113 | of true -> {some, Tag} | |
114 | ; false -> first_match(Tests, X) | |
115 | end. |