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/*
* RegexParser
*
*/
function RegexParser() {}
RegexParser.prototype.getRegex = function() { return this.regex }
RegexParser.prototype.getErrorMessage = function() { return this.errorMessage }
RegexParser.prototype.getErrorPosition = function() { return this.errorPosition }
RegexParser.prototype.lookahead = function() {
if (this.str.length > 0) {
return this.str.substring(0, 1);
}
return '';
}
RegexParser.prototype.consume = function(symbol) {
this.str = this.str.substring(1);
}
RegexParser.prototype.trymatch = function(symbol) {
if (this.str.substring(0, symbol.length) == symbol) {
this.consume(symbol);
return true;
}
return false;
}
RegexParser.prototype.match = function(symbol) {
if (!this.trymatch(symbol)) {
throw("Expected symbol '"+symbol+"'.");
}
}
RegexParser.prototype.isIn = function(symbol, set) {
if (symbol.length > 0) {
return set.indexOf(symbol) >= 0;
}
return false;
}
RegexParser.prototype.isLetter = function(symbol) {
return this.isIn(symbol, ALPHABET);
}
RegexParser.prototype.literal = function() {
var symbol = this.lookahead();
if(this.isLetter(symbol)) {
this.consume(symbol);
return new Nfa(symbol);
}
throw("Expected a letter or '"+EMPTYSYMBOL+"'.");
}
RegexParser.prototype.atom = function() {
if(this.trymatch('(')) {
var nfa = this.expr();
this.match(')');
return nfa;
}
return this.literal();
}
RegexParser.prototype.factor = function() {
return this.star(this.atom());
}
RegexParser.prototype.star = function(nfa) {
if (this.trymatch('*')) {
return this.star(nfa.kleene());
}
return nfa;
}
RegexParser.prototype.term = function() {
var nfa = this.factor();
var symbol = this.lookahead();
if (this.isLetter(symbol) || (symbol == '(')) {
return nfa.concat(this.term());
}
return nfa;
}
RegexParser.prototype.expr = function() {
var nfa = this.term();
if (this.trymatch('|')) {
return nfa.union(this.expr());
}
return nfa;
}
RegexParser.prototype.parse = function(regex) {
this.str = regex;
this.errorMessage = 'Ok'
this.errorPosition = -1;
var nfa = null;
try {
nfa = this.expr();
if(this.str.length > 0) {
throw('Supernumerous symbols.');
}
} catch(e) {
this.errorMessage = e;
this.errorPosition = regex.length - this.str.length;
nfa = null;
}
return nfa;
}
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