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%% Copyright (c) 2023 Peter Morgan <peter.james.morgan@gmail.com> |
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%% |
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%% Licensed under the Apache License, Version 2.0 (the "License"); |
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%% you may not use this file except in compliance with the License. |
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%% You may obtain a copy of the License at |
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%% |
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%% http://www.apache.org/licenses/LICENSE-2.0 |
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%% |
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%% Unless required by applicable law or agreed to in writing, software |
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%% distributed under the License is distributed on an "AS IS" BASIS, |
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%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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%% See the License for the specific language governing permissions and |
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%% limitations under the License. |
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%% @doc Parser combinators that deal with branches. |
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-module(scran_branch). |
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-feature(maybe_expr, enable). |
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-import(scran_sequence, [sequence/1]). |
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-export([alt/1]). |
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-export([permutation/1]). |
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-include_lib("kernel/include/logger.hrl"). |
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%% @doc Try each alternative parser in turn until one returns other |
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%% than nomatch (or none from optional/conditional parsers). |
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-spec alt([scran:parser()]) -> scran:parser(). |
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alt(Alternatives) -> |
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fun |
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(Input) -> |
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?FUNCTION_NAME(Alternatives, Input) |
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end. |
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-spec alt([scran:parser()], scran:input()) -> scran:result(). |
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alt([Alternative | Alternatives], Input) -> |
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?LOG_DEBUG(#{alternative => scran_debug:pp(Alternative), |
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input => Input}), |
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case Alternative(Input) of |
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{_, none} -> |
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%% condition or optional parser that has returned none, |
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%% continue parsing with remaining alternatives. |
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?LOG_DEBUG(#{nomatch => scran_debug:pp(Alternative)}), |
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?FUNCTION_NAME(Alternatives, Input); |
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{_, _} = Result -> |
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Result; |
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nomatch -> |
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?LOG_DEBUG(#{nomatch => scran_debug:pp(Alternative)}), |
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?FUNCTION_NAME(Alternatives, Input) |
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end; |
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alt([], _) -> |
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nomatch. |
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%% @doc Try each permutation of the supplied parsers until one returns |
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%% other than nomatch. |
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-spec permutation([scran:parser()]) -> scran:parser(). |
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permutation(Alternatives) -> |
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fun |
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(Input) -> |
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?FUNCTION_NAME(permutations(Alternatives), Input) |
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end. |
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-spec permutation([[scran:parser()]], unicode:chardata()) -> scran:result(). |
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permutation([Permutation | Permutations], Input) -> |
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maybe |
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{_, _} ?= (sequence(Permutation))(Input) |
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else |
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nomatch -> |
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?FUNCTION_NAME(Permutations, Input) |
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end; |
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permutation([], _) -> |
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nomatch. |
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-spec permutations([scran:parser()]) -> [[scran:parser()]]. |
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permutations([]) -> |
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[[]]; |
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permutations(L) -> |
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[[H | T] || H <- L, T <- ?FUNCTION_NAME(L -- [H])]. |