98 lines
4.2 KiB
JavaScript
98 lines
4.2 KiB
JavaScript
/*
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* Copyright (C) 2016 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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"use strict";
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// Loosely based on ECMA 55 sections 4-8, but loosened to allow for modern conventions, like
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// multi-character variable names. But this doesn't go too far - in particular, this doesn't do
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// unicode, because that would require more thought.
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function* lex(string)
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{
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let sourceLineNumber = 0;
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for (let line of string.split("\n")) {
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++sourceLineNumber;
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function consumeWhitespace()
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{
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if (/^\s+/.test(line))
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line = RegExp.rightContext;
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}
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function consume(kind)
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{
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line = RegExp.rightContext;
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return {kind, string: RegExp.lastMatch, sourceLineNumber, userLineNumber};
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}
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const isIdentifier = /^[a-z_]([a-z0-9_]*)/i;
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const isNumber = /^(([0-9]+(\.([0-9]*))?)|(\.[0-9]+)(e([+-]?)([0-9]+))?)/i;
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const isString = /^\"([^\"]|(\"\"))*\"/;
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const isKeyword = /^((base)|(data)|(def)|(dim)|(end)|(for)|(go)|(gosub)|(goto)|(if)|(input)|(let)|(next)|(on)|(option)|(print)|(randomize)|(read)|(restore)|(return)|(step)|(stop)|(sub)|(then)|(to))/i;
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const isOperator = /^(-|\+|\*|\/|\^|\(|\)|(<[>=]?)|(>=?)|=|,|\$|;)/;
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const isRem = /^rem\s.*/;
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consumeWhitespace();
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if (!/^[0-9]+/.test(line))
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throw new Error("At line " + sourceLineNumber + ": Expect line number: " + line);
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let userLineNumber = +RegExp.lastMatch;
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line = RegExp.rightContext;
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yield {kind: "userLineNumber", string: RegExp.lastMatch, sourceLineNumber, userLineNumber};
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consumeWhitespace();
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while (line.length) {
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if (isKeyword.test(line))
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yield consume("keyword");
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else if (isIdentifier.test(line))
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yield consume("identifier");
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else if (isNumber.test(line)) {
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let token = consume("number");
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token.value = +token.string;
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yield token;
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} else if (isString.test(line)) {
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let token = consume("string");
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token.value = "";
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for (let i = 1; i < token.string.length - 1; ++i) {
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let char = token.string.charAt(i);
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if (char == "\"")
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i++;
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token.value += char;
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}
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yield token;
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} else if (isOperator.test(line))
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yield consume("operator");
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else if (isRem.test(line))
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yield consume("remark");
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else
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throw new Error("At line " + sourceLineNumber + ": Cannot lex token: " + line);
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consumeWhitespace();
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}
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// Note: this is necessary for the parser, which may look-ahead without checking if we're
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// done. Fortunately, it won't look-ahead past a newLine.
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yield {kind: "newLine", string:"\n", sourceLineNumber, userLineNumber};
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}
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}
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