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| var rules = {
expression: function (tokens) {
var
result = rules.level1Expression(tokens),
token = tokens[0];
while (token && 'ADDSUB' === token.type) {
tokens.shift(); // consomme le token
switch (token.data) {
case '+':
result += rules.level1Expression(tokens);
break;
case '-':
result -= rules.level1Expression(tokens);
break;
}
token = tokens[0];
}
return result;
},
level1Expression: function (tokens) {
var
result = rules.level2Expression(tokens),
token = tokens[0];
while (token && 'MULDIV' === token.type) {
tokens.shift();
switch (token.data) {
case '*':
result *= rules.level2Expression(tokens);
break;
case '/':
result /= rules.level2Expression(tokens);
break;
}
token = tokens[0];
}
return result;
},
level2Expression: function (tokens) {
var
token = tokens[0],
result;
if (!token) {
throwError('level2Expression', null, 'LEFTPAR, FUNC, NUM ou CONST');
}
switch (token.type) {
case 'LEFTPAR':
tokens.shift();
result = rules.expression(tokens);
if (!tokens[0] || 'RIGHTPAR' !== tokens[0].type) {
throwError('level2Expression', tokens[0], 'RIGHTPAR');
}
tokens.shift();
break;
case 'FUNC':
result = rules.functionCall(tokens);
break;
case 'NUM':
case 'CONST':
result = rules.primitive(tokens);
break;
default:
throwError('level2Expression', token, 'LEFTPAR, FUNC, NUM ou CONST');
}
return result;
},
functionCall: function (tokens) {
var
funcToken,
func,
exprResult;
if (!tokens[0] || 'FUNC' !== tokens[0].type) {
throwError('functionCall', tokens[0], 'FUNC');
}
funcToken = tokens.shift();
func = function (x) {
return Math[funcToken.data.toLowerCase()](x);
};
if (!tokens[0] || 'LEFTPAR' !== tokens[0].type) {
throwError('functionCall', tokens[0], 'LEFTPAR');
}
tokens.shift();
exprResult = rules.expression(tokens);
if (!tokens[0] || 'RIGHTPAR' !== tokens[0].type) {
throwError('functionCall', tokens[0], 'RIGHTPAR');
}
tokens.shift();
return func(exprResult);
},
primitive: function (tokens) {
var
result,
token = tokens[0];
if (!token) {
throwError('primitive', token, 'NUM ou CONST');
}
switch (token.type) {
case 'NUM':
tokens.shift();
result = parseFloat(token.data.replace(',', '.'));
break;
case 'CONST':
tokens.shift();
switch (token.data.toLowerCase()) {
case 'g':
result = 9.81;
break;
case 'pi':
result = Math.PI;
break;
default:
throw new Error('Constante ' + token.data + ' non implémentée');
break;
}
break;
default:
throwError('primitive', token, 'NUM ou CONST');
break;
}
return result;
}
};
function throwError(ruleName, token, expected) {
if (token) {
throw new Error(ruleName + ': token inattendu ' +
token.type + ' "' + token.data + '"; ' +
expected + ' était attendu');
}
else {
throw new Error(ruleName + ': plus de tokens; ' +
expected + ' était attendu');
}
}
function parseTokens(tokenList) {
var result = rules.expression(tokenList);
if (tokenList.length > 0) {
throw new Error('Erreur de syntaxe : "' +
tokenList[0].data + '" inattendu');
}
return result;
}
function parse(text) {
var tokens = lex(text);
return parseTokens(tokens);
} |
