162 lines
3.9 KiB
JavaScript
162 lines
3.9 KiB
JavaScript
var readSchemeExpressions;
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function tokenize(s) {
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function replaceEscapes(s) {
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return s.replace(/\\./g, function(match, submatch, index) {
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// FIXME: add more escape sequences.
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if (match == '\\n') {
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return "\n";
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}
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else {
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return match.substring(1);
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}
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});
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}
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var tokens = [];
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var PATTERNS = [['whitespace' , /^(\s+)/],
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['comment' , /(^;[^\n]*)/],
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['(' , /^(\(|\[)/],
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[')' , /^(\)|\])/],
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['\'' , /^(\')/],
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['`' , /^(`)/],
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[',' , /^(,)/],
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['char', /^\#\\(newline)/],
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['char', /^\#\\(.)/],
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['number' , /^([+\-]?(?:\d+\.\d+|\d+\.|\.\d+|\d+))/],
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['string' , /^"((?:([^\\"]|(\\.)))*)"/], // comment (emacs getting confused with quote): "
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['symbol' ,/^([a-zA-Z\:\+\=\~\_\?\!\@\#\$\%\^\&\*\-\/\.\>\<][\w\:\+\=\~\_\?\!\@\#\$\%\^\&\*\-\/\.\>\<]*)/]
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];
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while (true) {
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var shouldContinue = false;
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for (var i = 0; i < PATTERNS.length; i++) {
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var patternName = PATTERNS[i][0];
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var pattern = PATTERNS[i][1]
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var result = s.match(pattern);
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if (result != null) {
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if (patternName == 'string') {
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result[1] = replaceEscapes(result[1]);
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}
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if (patternName != 'whitespace' && patternName != 'comment') {
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tokens.push([patternName, result[1]]);
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}
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s = s.substring(result[0].length);
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shouldContinue = true;
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}
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}
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if (! shouldContinue) {
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break;
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}
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}
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return [tokens, s];
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}
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(function(){
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readSchemeExpressions = function(s) {
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var tokensAndError = tokenize(s);
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var tokens = tokensAndError[0];
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if (tokensAndError[1].length > 0) {
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throw new Error("Error while tokenizing: the rest of the stream is: " + tokensAndError[1]);
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}
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var quoteSymbol = plt.types.Symbol.makeInstance("quote");
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var quasiquoteSymbol = plt.types.Symbol.makeInstance("quasiquote");
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var unquoteSymbol = plt.types.Symbol.makeInstance("unquote");
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var empty = plt.types.Empty.EMPTY;
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function isType(type) {
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return (tokens.length > 0 && tokens[0][0] == type);
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}
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function eat(expectedType) {
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if (tokens.length == 0)
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throw new Error("token stream exhausted while trying to eat " +
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expectedType);
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var t = tokens.shift();
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if (t[0] == expectedType) {
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return t;
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} else {
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throw new Error("Unexpected token " + t);
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}
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}
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function readExpr() {
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var t;
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if (isType('(')) {
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eat('(');
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var result = readExprs();
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eat(')');
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return result;
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} else if (isType("'")) {
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eat("'");
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var quoted = readExpr();
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return plt.Kernel.cons(quoteSymbol,
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plt.Kernel.cons(quoted, empty));
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} else if (isType('`')) {
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eat("`");
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return plt.Kernel.cons(quasiquoteSymbol,
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plt.kernel.cons(quoted, empty));
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} else if (isType(',')) {
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eat(",");
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return plt.Kernel.cons(unquoteSymbol,
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plt.kernel.cons(quoted, empty));
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} else if (isType('number')) {
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t = eat('number');
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if (t[1].match(/\./)) {
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return plt.types.FloatPoint.makeInstance(parseFloat(t[1]));
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} else {
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return plt.types.Rational.makeInstance(parseInt(t[1]), 1);
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}
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} else if (isType('string')) {
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t = eat('string');
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return plt.types.String.makeInstance(t[1]);
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} else if (isType('char')) {
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t = eat('char');
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if (t[1] == 'newline') {
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return plt.types.Char.makeInstance('\n');
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}
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else {
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return plt.types.Char.makeInstance(t[1]);
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}
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} else if (isType('symbol')) {
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t = eat('symbol');
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return plt.types.Symbol.makeInstance(t[1]);
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} else {
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throw new Error("Parse broke with token stream " + tokens);
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}
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}
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function readExprs() {
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var result = plt.types.Empty.EMPTY;
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while (true) {
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if (tokens.length == 0 || isType(')')) {
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break;
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} else {
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var nextElt = readExpr();
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result = plt.types.Cons.makeInstance(nextElt, result);
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}
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}
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return plt.Kernel.reverse(result);
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}
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return readExprs();
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}
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}());
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