74 lines
1.1 KiB
JavaScript
74 lines
1.1 KiB
JavaScript
/**
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* The MIT License (MIT)
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* Copyright (c) 2017-present Dmitry Soshnikov <dmitry.soshnikov@gmail.com>
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*/
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'use strict';
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/**
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* A regexp-tree plugin to replace different range-based quantifiers
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* with their symbol equivalents.
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*
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* a{0,} -> a*
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* a{1,} -> a+
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* a{1} -> a
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*
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* NOTE: the following is automatically handled in the generator:
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*
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* a{3,3} -> a{3}
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*/
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module.exports = {
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Quantifier: function Quantifier(path) {
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var node = path.node;
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if (node.kind !== 'Range') {
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return;
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}
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// a{0,} -> a*
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rewriteOpenZero(path);
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// a{1,} -> a+
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rewriteOpenOne(path);
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// a{1} -> a
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rewriteExactOne(path);
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}
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};
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function rewriteOpenZero(path) {
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var node = path.node;
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if (node.from !== 0 || node.to) {
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return;
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}
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node.kind = '*';
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delete node.from;
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}
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function rewriteOpenOne(path) {
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var node = path.node;
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if (node.from !== 1 || node.to) {
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return;
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}
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node.kind = '+';
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delete node.from;
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}
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function rewriteExactOne(path) {
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var node = path.node;
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if (node.from !== 1 || node.to !== 1) {
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return;
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}
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path.parentPath.replace(path.parentPath.node.expression);
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} |