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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 |
a6244ba2 SK |
13 | ]). |
14 | ||
15 | ||
781f182f | 16 | -define(DEFAULT_RECURSION_LIMIT, 1000). |
ff793acf SK |
17 | |
18 | ||
a6244ba2 SK |
19 | -type t(A) :: |
20 | [A]. | |
21 | ||
22 | ||
ff793acf SK |
23 | %% @doc Tail-recursive equivalent of lists:map/2 |
24 | %% @end | |
25 | -spec map([A], fun((A) -> (B))) -> | |
26 | [B]. | |
27 | map(Xs, F) -> | |
781f182f | 28 | map(Xs, F, ?DEFAULT_RECURSION_LIMIT). |
ff793acf | 29 | |
781f182f | 30 | -spec map([A], fun((A) -> (B)), RecursionLimit :: non_neg_integer()) -> |
ff793acf | 31 | [B]. |
781f182f SK |
32 | map(Xs, F, RecursionLimit) -> |
33 | map(Xs, F, RecursionLimit, 0). | |
34 | ||
35 | map([], _, _, _) -> | |
ff793acf | 36 | []; |
781f182f | 37 | map([X1], F, _, _) -> |
ff793acf SK |
38 | Y1 = F(X1), |
39 | [Y1]; | |
781f182f | 40 | map([X1, X2], F, _, _) -> |
ff793acf SK |
41 | Y1 = F(X1), |
42 | Y2 = F(X2), | |
43 | [Y1, Y2]; | |
781f182f | 44 | map([X1, X2, X3], F, _, _) -> |
ff793acf SK |
45 | Y1 = F(X1), |
46 | Y2 = F(X2), | |
47 | Y3 = F(X3), | |
48 | [Y1, Y2, Y3]; | |
781f182f | 49 | map([X1, X2, X3, X4], F, _, _) -> |
ff793acf SK |
50 | Y1 = F(X1), |
51 | Y2 = F(X2), | |
52 | Y3 = F(X3), | |
53 | Y4 = F(X4), | |
54 | [Y1, Y2, Y3, Y4]; | |
781f182f | 55 | map([X1, X2, X3, X4, X5 | Xs], F, RecursionLimit, RecursionCount) -> |
ff793acf SK |
56 | Y1 = F(X1), |
57 | Y2 = F(X2), | |
58 | Y3 = F(X3), | |
59 | Y4 = F(X4), | |
60 | Y5 = F(X5), | |
61 | Ys = | |
781f182f | 62 | case RecursionCount > RecursionLimit |
ff793acf | 63 | of true -> map_slow(Xs, F) |
781f182f | 64 | ; false -> map (Xs, F, RecursionLimit, RecursionCount + 1) |
ff793acf SK |
65 | end, |
66 | [Y1, Y2, Y3, Y4, Y5 | Ys]. | |
67 | ||
68 | ||
2a81fbac SK |
69 | %% @doc lists:reverse(map_rev(L, F)) |
70 | %% @end | |
71 | -spec map_slow([A], fun((A) -> (B))) -> | |
72 | [B]. | |
73 | map_slow(Xs, F) -> | |
74 | lists:reverse(map_rev(Xs, F)). | |
75 | ||
76 | ||
5e20a667 SK |
77 | %% @doc Tail-recursive alternative to lists:map/2, which accumulates and |
78 | %% returns list in reverse order. | |
c66ddf80 SK |
79 | %% @end |
80 | -spec map_rev([A], fun((A) -> (B))) -> | |
81 | [B]. | |
82 | map_rev(Xs, F) -> | |
83 | map_rev_acc(Xs, F, []). | |
84 | ||
85 | -spec map_rev_acc([A], fun((A) -> (B)), [B]) -> | |
86 | [B]. | |
87 | map_rev_acc([], _, Ys) -> | |
88 | Ys; | |
89 | map_rev_acc([X|Xs], F, Ys) -> | |
90 | Y = F(X), | |
91 | map_rev_acc(Xs, F, [Y|Ys]). | |
92 | ||
93 | ||
a6244ba2 SK |
94 | -spec unique_preserve_order(t(A)) -> |
95 | t(A). | |
96 | unique_preserve_order(L) -> | |
17b5d686 | 97 | PrependIfNew = |
a6244ba2 SK |
98 | fun (X, Xs) -> |
99 | case lists:member(X, Xs) | |
17b5d686 SK |
100 | of true -> Xs |
101 | ; false -> [X | Xs] | |
a6244ba2 SK |
102 | end |
103 | end, | |
17b5d686 | 104 | lists:reverse(lists:foldl(PrependIfNew, [], L)). |