2020-06-03 22:24:41 +08:00
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function lexer(str) {
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str = str.toLowerCase();
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const expressionTokens = [];
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let quotes = false;
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let currentWord = '';
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function isOperatorSymbol(chr) {
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return ['=', '*', '>', '<', '!'].includes(chr);
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}
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function previousOperatorSymbol() {
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if (currentWord.length === 0) {
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return false;
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}
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else {
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return isOperatorSymbol(currentWord[currentWord.length - 1]);
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}
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}
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function finishWord() {
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if (currentWord === '') {
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return;
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}
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2020-06-03 23:11:03 +08:00
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expressionTokens.push(currentWord);
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2020-06-03 22:24:41 +08:00
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currentWord = '';
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}
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for (let i = 0; i < str.length; i++) {
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const chr = str[i];
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if (chr === '\\') {
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if ((i + 1) < str.length) {
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i++;
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currentWord += str[i];
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}
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else {
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currentWord += chr;
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}
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continue;
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}
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else if (['"', "'", '`'].includes(chr)) {
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if (!quotes) {
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2020-06-03 23:11:03 +08:00
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if (previousOperatorSymbol()) {
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finishWord();
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2020-06-03 22:24:41 +08:00
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}
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2020-06-03 23:11:03 +08:00
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quotes = chr;
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2020-06-03 22:24:41 +08:00
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}
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else if (quotes === chr) {
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quotes = false;
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finishWord();
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}
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else {
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// it's a quote but within other kind of quotes so it's valid as a literal character
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currentWord += chr;
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}
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continue;
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}
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else if (!quotes) {
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if (currentWord.length === 0 && (chr === '#' || chr === '~')) {
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currentWord = chr;
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continue;
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}
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else if (chr === ' ') {
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finishWord();
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continue;
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}
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2020-06-03 23:11:03 +08:00
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else if (['(', ')', '.'].includes(chr)) {
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2020-06-03 22:24:41 +08:00
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finishWord();
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currentWord += chr;
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finishWord();
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continue;
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}
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2020-06-03 23:11:03 +08:00
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else if (previousOperatorSymbol() !== isOperatorSymbol(chr)) {
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2020-06-03 22:24:41 +08:00
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finishWord();
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currentWord += chr;
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continue;
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}
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}
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currentWord += chr;
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}
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finishWord();
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2020-06-03 23:11:03 +08:00
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return expressionTokens;
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2020-06-03 22:24:41 +08:00
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}
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export default {
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lexer
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}
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