| 1 | %%%---------------------------------------------------------------------------- |
| 2 | %%% Equivalent to stdlib's orddict, but with a pretty (IMO), uniform interface. |
| 3 | %%%---------------------------------------------------------------------------- |
| 4 | -module(hope_kv_list). |
| 5 | |
| 6 | -behavior(hope_dictionary). |
| 7 | |
| 8 | -export_type( |
| 9 | [ t/2 |
| 10 | ]). |
| 11 | |
| 12 | -export( |
| 13 | [ empty/0 |
| 14 | , get/2 |
| 15 | , set/3 |
| 16 | , update/3 |
| 17 | , pop/2 |
| 18 | , iter/2 |
| 19 | , map/2 |
| 20 | , filter/2 |
| 21 | , fold/3 |
| 22 | , of_kv_list/1 |
| 23 | , to_kv_list/1 |
| 24 | ]). |
| 25 | |
| 26 | |
| 27 | -type t(K, V) :: |
| 28 | [{K, V}]. |
| 29 | |
| 30 | |
| 31 | %% ============================================================================ |
| 32 | %% API |
| 33 | %% ============================================================================ |
| 34 | |
| 35 | -spec empty() -> |
| 36 | []. |
| 37 | empty() -> |
| 38 | []. |
| 39 | |
| 40 | get(T, K) -> |
| 41 | case lists:keyfind(K, 1, T) |
| 42 | of false -> none |
| 43 | ; {K, V} -> {some, V} |
| 44 | end. |
| 45 | |
| 46 | set(T, K, V) -> |
| 47 | lists:keystore(K, 1, T, {K, V}). |
| 48 | |
| 49 | update(T, K, F) -> |
| 50 | V1Opt = get(T, K), |
| 51 | V2 = F(V1Opt), |
| 52 | % TODO: Eliminate the 2nd lookup. |
| 53 | set(T, K, V2). |
| 54 | |
| 55 | pop(T1, K) -> |
| 56 | case lists:keytake(K, 1, T1) |
| 57 | of {value, {K, V}, T2} -> {{some, V}, T2} |
| 58 | ; false -> {none , T1} |
| 59 | end. |
| 60 | |
| 61 | iter(T, F1) -> |
| 62 | F2 = lift_map(F1), |
| 63 | lists:foreach(F2, T). |
| 64 | |
| 65 | map(T, F1) -> |
| 66 | F2 = fun ({K, _}=X) -> {K, apply_map(F1, X)} end, |
| 67 | lists:map(F2, T). |
| 68 | |
| 69 | filter(T, F1) -> |
| 70 | F2 = lift_map(F1), |
| 71 | lists:filter(F2, T). |
| 72 | |
| 73 | fold(T, F1, Accumulator) -> |
| 74 | F2 = fun ({K, V}, Acc) -> F1(K, V, Acc) end, |
| 75 | lists:foldl(F2, Accumulator, T). |
| 76 | |
| 77 | to_kv_list(T) -> |
| 78 | T. |
| 79 | |
| 80 | of_kv_list(List) -> |
| 81 | % TODO: Decide if validation is to be done here. Do so if yes. |
| 82 | List. |
| 83 | |
| 84 | |
| 85 | %% ============================================================================ |
| 86 | %% Helpers |
| 87 | %% ============================================================================ |
| 88 | |
| 89 | -spec lift_map(F) -> |
| 90 | G |
| 91 | when F :: fun(( K, V1 ) -> V2) |
| 92 | , G :: fun(({K, V1}) -> V2) |
| 93 | . |
| 94 | lift_map(F) -> |
| 95 | fun (X) -> apply_map(F, X) end. |
| 96 | |
| 97 | -spec apply_map(fun((K, V1) -> V2), {K, V1}) -> |
| 98 | V2. |
| 99 | apply_map(F, {K, V}) -> |
| 100 | F(K, V). |