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ll1.html
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<html>
<head>
<title>LL(1) Parser Generator</title>
<style>
body * { font-family: courier; }
td { horizontal-align: middle; vertical-align: middle; }
.tree td { vertical-align: top; }
</style>
</head>
<body>
<script language="javascript">
function $(id) {
return document.getElementById(id);
}
var EPSILON = '\'\'';
var alphabet;
var nonterminals;
var terminals;
var rules;
var firsts;
var follows;
var ruleTable;
function grammarChanged() {
$('llTableRows').innerHTML = '';
rules = $('grammar').value.split('\n');
alphabet = [];
nonterminals = [];
terminals = [];
collectAlphabetAndNonterminalsAndTerminals();
collectFirsts();
collectFollows();
makeRuleTable();
displayTable();
parseInput();
}
function displayTable() {
$('llTableHead').innerHTML = "<th>FIRST</th><th>FOLLOW</th><th>Nonterminal</th>";
for (var i in terminals) {
$('llTableHead').innerHTML += "<th>" + terminals[i] + "</th>";
}
$('llTableHead').innerHTML += "<th>$</th>";
for (var i in nonterminals) {
var nonterminal = nonterminals[i];
var s = "<tr>";
s += "<tr>";
s += "<td nowrap=\"nowrap\">{" + firsts[nonterminal] + "}</td><td nowrap=\"nowrap\">{" + follows[nonterminal] + "}</td><td nowrap=\"nowrap\">" + nonterminal + "</td>";
for (var j in terminals) {
s += "<td nowrap=\"nowrap\">" + emptyIfUndefined(ruleTable[nonterminal][terminals[j]]) + "</td>";
}
s += "<td nowrap=\"nowrap\">" + emptyIfUndefined(ruleTable[nonterminal]['$']) + "</td>";
s += "</tr>";
$('llTableRows').innerHTML += s;
}
}
function makeRuleTable() {
ruleTable = new Object();
for (var i in rules) {
var rule = rules[i].trim().split('->');
if (rule.length < 2) {
continue;
}
var nonterminal = rule[0].trim();
var development = trimElements(rule[1].trim().split(' '));
var developmentFirsts = collectFirsts3(development);
for (var j in developmentFirsts) {
var symbol = developmentFirsts[j];
if (symbol != EPSILON) {
if (ruleTable[nonterminal] == undefined) {
ruleTable[nonterminal] = new Object();
}
var oldTableRule = ruleTable[nonterminal][symbol];
if (oldTableRule == undefined) {
ruleTable[nonterminal][symbol] = rules[i].trim();
} else {
ruleTable[nonterminal][symbol] = oldTableRule + "<br>" + rules[i].trim();
}
} else {
for (var j in follows[nonterminal]) {
var symbol2 = follows[nonterminal][j];
if (ruleTable[nonterminal] == undefined) {
ruleTable[nonterminal] = new Object();
}
var oldTableRule = ruleTable[nonterminal][symbol2];
if (oldTableRule == undefined) {
ruleTable[nonterminal][symbol2] = rules[i].trim();
} else {
ruleTable[nonterminal][symbol2] = oldTableRule + "<br>" + rules[i].trim();
}
}
}
}
}
}
function emptyIfUndefined(string) {
return string == undefined ? '' : string;
}
function collectFirsts() {
firsts = new Object();
var notDone;
do {
notDone = false;
for (var i in rules) {
var rule = rules[i].split('->');
if (rule.length < 2) {
continue;
}
var nonterminal = rule[0].trim();
var development = trimElements(rule[1].trim().split(' '));
var nonterminalFirsts = firsts[nonterminal];
if (nonterminalFirsts == undefined) {
nonterminalFirsts = [];
}
if (development.length == 1 && development[0] == EPSILON) {
notDone |= addUnique(EPSILON, nonterminalFirsts);
} else {
notDone |= collectFirsts4(development, nonterminalFirsts);
}
firsts[nonterminal] = nonterminalFirsts;
}
} while (notDone);
}
/**
* @param development
* <br>Array of symbols
* @param nonterminalFirsts
* <br>Array of symbols
* <br>Input-output
* @return <code>true</code> If <code>nonterminalFirsts</code> has been modified
*/
function collectFirsts4(development, nonterminalFirsts) {
var result = false;
var epsilonInSymbolFirsts = true;
for (var j in development) {
var symbol = development[j];
epsilonInSymbolFirsts = false;
if (isElement(symbol, terminals)) {
result |= addUnique(symbol, nonterminalFirsts);
break;
}
for (var k in firsts[symbol]) {
var first = firsts[symbol][k];
epsilonInSymbolFirsts |= first == EPSILON;
if(first !== EPSILON)
result |= addUnique(first, nonterminalFirsts);
}
if (!epsilonInSymbolFirsts) {
break;
}
}
if (epsilonInSymbolFirsts) {
result |= addUnique(EPSILON, nonterminalFirsts);
}
return result;
}
/**
* @param sequence
* <br>Array of symbols
*/
function collectFirsts3(sequence) {
var result = [];
var epsilonInSymbolFirsts = true;
for (var j in sequence) {
var symbol = sequence[j];
epsilonInSymbolFirsts = false;
if (isElement(symbol, terminals)) {
addUnique(symbol, result);
break;
}
for (var k in firsts[symbol]) {
var first = firsts[symbol][k];
epsilonInSymbolFirsts |= first == EPSILON;
if(first !== EPSILON)
addUnique(first, result);
}
epsilonInSymbolFirsts |= firsts[symbol] == undefined || firsts[symbol].length == 0;
if (!epsilonInSymbolFirsts) {
break;
}
}
if (epsilonInSymbolFirsts) {
addUnique(EPSILON, result);
}
return result;
}
function collectFollows() {
follows = new Object();
var notDone;
do {
notDone = false;
for (var i in rules) {
var rule = rules[i].split('->');
if (rule.length < 2) {
continue;
}
var nonterminal = rule[0].trim();
var development = trimElements(rule[1].trim().split(' '));
if (i == 0) {
var nonterminalFollows = follows[nonterminal];
if (nonterminalFollows == undefined) {
nonterminalFollows = [];
}
notDone |= addUnique('$', nonterminalFollows);
follows[nonterminal] = nonterminalFollows;
}
for (var j in development) {
var symbol = development[j];
if (isElement(symbol, nonterminals)) {
var symbolFollows = follows[symbol];
if (symbolFollows == undefined) {
symbolFollows = [];
}
var afterSymbolFirsts = collectFirsts3(development.slice(parseInt(j) + 1));
for (var k in afterSymbolFirsts) {
var first = afterSymbolFirsts[k];
if (first == EPSILON) {
var nonterminalFollows = follows[nonterminal];
for (var l in nonterminalFollows) {
notDone |= addUnique(nonterminalFollows[l], symbolFollows);
}
} else {
notDone |= addUnique(first, symbolFollows);
}
}
follows[symbol] = symbolFollows;
}
}
}
} while (notDone);
}
function collectAlphabetAndNonterminalsAndTerminals() {
for (var i in rules) {
var rule = rules[i].split('->');
if (rule.length != 2) {
continue;
}
var nonterminal = rule[0].trim();
var development = trimElements(rule[1].trim().split(' '));
addUnique(nonterminal, alphabet);
addUnique(nonterminal, nonterminals);
for (var j in development) {
var symbol = development[j];
if (symbol != EPSILON) {
addUnique(symbol, alphabet);
}
}
}
subtract(alphabet, nonterminals, terminals);
}
/**
* @param result
* <br>Array
* <br>Input-output
* @return <code>result</code>
*/
function subtract(array1, array2, result) {
for (var i in array1) {
var element = array1[i];
if (!isElement(element, array2)) {
result[result.length] = element;
}
}
return result;
}
/**
* @return
* <br>Array
* <br>New
*/
function trimElements(array) {
var result = [];
for (var i in array) {
result[i] = array[i].trim();
}
return result;
}
function isElement(element, array) {
for (var i in array) {
if (element == array[i]) {
return true;
}
}
return false;
}
/**
* @param array
* <br>Input-output
* @return <code>true</code> iff <code>array</code> has been modified
*/
function addUnique(element, array) {
if (!isElement(element, array)) {
array[array.length] = element;
return true;
}
return false;
}
function resize(textInput, minimumSize) {
textInput.size = Math.max(minimumSize, textInput.value.length);
}
function parseInput() {
var input = $('input').value.trim().split(' ');
var stack = ['$', nonterminals[0]];
var parsingRows = '<tr><td nowrap=\"nowrap\">' + stack.join(' ') + "</td><td nowrap=\"nowrap\">" + input.join(' ') + " $</td nowrap=\"nowrap\"><td></td></tr>\n";
var maximumStepCount = parseInt($('maximumStepCount').value);
var ok = true;
var tree = new Object();
tree.label = 'root';
tree.children = [];
var parents = [tree];
for (var i = 0, index = 0; i < maximumStepCount && 1 < stack.length; ++i) {
var stackTop = stack[stack.length - 1];
var symbol = index < input.length ? input[index] : '$';
if (symbol.trim() == '') {
symbol = '$';
}
var rule = '';
if (stackTop == symbol) {
stack.pop();
++index;
parents.pop().children.push(symbol);
} else {
if (isElement(stackTop, nonterminals)) {
rule = ruleTable[stackTop][symbol];
var node = new Object();
node.label = stackTop;
node.children = [];
parents.pop().children.push(node);
if (rule == undefined) {
ok = false;
break;
}
stack.pop();
var reverseDevelopment = rule.split('->')[1].trim().split(' ').slice(0).reverse();
for (var i in reverseDevelopment) {
parents.push(node);
}
if (!isElement(EPSILON, reverseDevelopment)) {
stack = stack.concat(reverseDevelopment);
} else {
parents.pop().children.push(EPSILON);
}
} else {
ok = false;
break;
}
}
parsingRows += '<tr><td nowrap=\"nowrap\">' + stack.join(' ') + "</td><td nowrap=\"nowrap\">" + input.slice(index).join(' ') + " $</td><td nowrap=\"nowrap\">" + rule + "</td></tr>\n";
}
$('parsingTableRows').innerHTML = parsingRows;
$('input').style.color = ok ? 'green' : 'red';
$('tree').innerHTML = ok ? toString(tree.children[0]) : '';
}
function toString(tree) {
if (tree.label == undefined) {
return '' + tree;
}
var result = "<table class=\"tree\" border=\"1\"><thead><tr><th colspan=\"" + tree.children.length + "\">" + tree.label + "</th></tr></thead><tbody><tr>";
for (var i in tree.children) {
result += "<td>" + toString(tree.children[i]) + "</td>";
}
result += "</tr></tbody></table>";
return result;
}
// -->
</script>
<table><tbody><tr>
<td>
<div>LL(1) grammar ('' is ε):</div>
<textarea id="grammar" rows="10" cols="20" onchange="grammarChanged();">E -> T E'
E' -> + T E'
E' -> ''
T -> F T'
T' -> * F T'
T' -> ''
F -> ( E )
F -> id
</textarea>
</td>
<td>
<input type="button" value=">>">
</td>
<td>
<div>
<table border="1"><thead><tr id="llTableHead">
<th>FIRST</th><th>FOLLOW</th><th>Nonterminal</th>
</tr></thead><tbody id="llTableRows">
</tbody></table>
</div>
</td>
</tr></tbody></table>
<p>Maximum number of steps: <input id="maximumStepCount" type="text" size="3" onkeyup="resize(this, 3);" onchange="parseInput();" value="100"></p>
<p>Input (tokens): <input id="input" type="text" size="10" onkeyup="resize(this, 10);" onchange="parseInput();" value="id + id"></p>
<p><input type="button" value="GO!"></p>
<br>
<table border="8"><thead><tr><th>Trace</th><th>Tree</th></tr></thead><tbody><tr><td>
<table border="1"><thead><tr><th>Stack</th><th>Input</th><th>Rule</th>
</tr></thead><tbody id="parsingTableRows">
</tbody></table>
</td><td style="vertical-align: top;">
<div id="tree"></div>
</td></tr></tbody></table>
</body>
<script language="javascript">
grammarChanged();
</script>
</html>