/**
* Parse a factor.
*
* @param token the initial token.
* @return the root of the generated parse subtree.
* @throws Exception if an error occurred.
*/
private ICodeNode parseFactor(Token token) throws Exception {
TokenType tokenType = token.getType();
ICodeNode rootNode = null;
switch ((PascalTokenType) tokenType) {
case IDENTIFIER:
{
return parseIdentifier(token);
}
case INTEGER:
{
// Create an INTEGER_CONSTANT node as the root node
rootNode = ICodeFactory.createICodeNode(INTEGER_CONSTANT);
rootNode.setAttribute(VALUE, token.getValue());
token = nextToken(); // consume the number
rootNode.setTypeSpec(Predefined.integerType);
break;
}
case REAL:
{
// Create an REAL_CONSTANT node as the root node.
rootNode = ICodeFactory.createICodeNode(REAL_CONSTANT);
rootNode.setAttribute(VALUE, token.getValue());
token = nextToken(); // consume the number
rootNode.setTypeSpec(Predefined.realType);
break;
}
case STRING:
{
String value = (String) token.getValue();
// Create a STRING_CONSTANT node as the root node.
rootNode = ICodeFactory.createICodeNode(STRING_CONSTANT);
rootNode.setAttribute(VALUE, value);
TypeSpec resultType =
value.length() == 1 ? Predefined.charType : TypeFactory.createStringType(value);
token = nextToken(); // consume the string
rootNode.setTypeSpec(resultType);
break;
}
case NOT:
{
token = nextToken(); // consume the NOT
// Create a NOT node as the root node.
rootNode = ICodeFactory.createICodeNode(ICodeNodeTypeImpl.NOT);
// Parse the factor. The NOT node adopts the factor node as its child.
ICodeNode factorNode = parseFactor(token);
rootNode.addChild(factorNode);
// Type check: the factor must be boolean.
TypeSpec factorType =
factorNode != null ? factorNode.getTypeSpec() : Predefined.undefinedType;
if (!TypeChecker.isBoolean(factorType))
errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
rootNode.setTypeSpec(Predefined.booleanType);
break;
}
case LEFT_PAREN:
{
token = nextToken(); // consume the (
// Parse an expression and make its node the root node.
rootNode = parseExpression(token);
TypeSpec resultType =
rootNode != null ? rootNode.getTypeSpec() : Predefined.undefinedType;
// Look for the matching ) token.
token = currentToken();
if (token.getType() == RIGHT_PAREN) token = nextToken(); // consume the )
else errorHandler.flag(token, MISSING_RIGHT_PAREN, this);
rootNode.setTypeSpec(resultType);
break;
}
default:
{
errorHandler.flag(token, UNEXPECTED_TOKEN, this);
break;
}
}
return rootNode;
}
