/**
* Parse a term.
*
* @param token the initial token.
* @return the root of the generated parse subtree.
* @throws Exception if an error occurred.
*/
private ICodeNode parseTerm(Token token) throws Exception {
// Parse a factor and makes its node the root node.
ICodeNode rootNode = parseFactor(token);
TypeSpec resultType = rootNode != null ? rootNode.getTypeSpec() : Predefined.undefinedType;
token = currentToken();
TokenType tokenType = token.getType();
// Loop over multiplicative operators.
while (MULT_OPS.contains(tokenType)) {
TokenType operator = tokenType;
// Create a new operator node and adopt the current tree as its first child.
ICodeNodeType nodeType = MULT_OPS_OPS_MAP.get(operator);
ICodeNode opNode = ICodeFactory.createICodeNode(nodeType);
opNode.addChild(rootNode);
token = nextToken(); // consume the operator
// Parse another factor.
// The operator node adopts the term's tree as its secomd child.
ICodeNode factorNode = parseFactor(token);
opNode.addChild(factorNode);
TypeSpec factorType =
factorNode != null ? factorNode.getTypeSpec() : Predefined.undefinedType;
// The operator node becomes the new root node.
rootNode = opNode;
// Determine the result type.
switch ((PascalTokenType) operator) {
case STAR:
{
// Both operands integer ==> integer result.
if (TypeChecker.areBothInteger(resultType, factorType)) {
resultType = Predefined.integerType;
}
// Both real operands or one real and one integer operand
// ==> real result.
else if (TypeChecker.isAtLeastOneReal(resultType, factorType)) {
resultType = Predefined.realType;
} else {
errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
}
break;
}
case SLASH:
{
// All integer and real operand combinations
// ==> real result.
if (TypeChecker.areBothInteger(resultType, factorType)
|| TypeChecker.isAtLeastOneReal(resultType, factorType)) {
resultType = Predefined.realType;
} else {
errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
}
break;
}
case DIV:
case MOD:
{
// Both operands integer ==> integer result.
if (TypeChecker.areBothInteger(resultType, factorType)) {
resultType = Predefined.integerType;
} else {
errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
}
break;
}
case AND:
{
// Both operands boolean ==> boolean result.
if (TypeChecker.areBothBoolean(resultType, factorType)) {
resultType = Predefined.booleanType;
} else {
errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
}
break;
}
}
// The operator node becomes the new root node.
rootNode.setTypeSpec(resultType);
token = currentToken();
tokenType = token.getType();
}
return rootNode;
}
/**
* Parse a simple expression.
*
* @param token the initial token.
* @return the root of the generated parse subtree.
* @throws Exception if an error occurred.
*/
private ICodeNode parseSimpleExpression(Token token) throws Exception {
Token signToken = null;
TokenType signType = null; // type of leading sign (if any)
// Look for a leading + or - sign
TokenType tokenType = token.getType();
if ((tokenType == PLUS) || (tokenType == MINUS)) {
signType = tokenType;
signToken = token;
token = nextToken(); // consume the + or -
}
// Parse a term and make the root of its tree the root node.
ICodeNode rootNode = parseTerm(token);
TypeSpec resultType = rootNode != null ? rootNode.getTypeSpec() : Predefined.undefinedType;
// Type check: Leading sign.
if ((signType != null) && (!TypeChecker.isIntegerOrReal(resultType)))
errorHandler.flag(signToken, INCOMPATIBLE_TYPES, this);
// Was there a leading - sign?
if (signType == MINUS) {
// Create a NEGATE node and adopt the current tree as its child.
// The NEGATE node becomes the new root node.
ICodeNode negateNode = ICodeFactory.createICodeNode(NEGATE);
negateNode.addChild(rootNode);
negateNode.setTypeSpec(rootNode.getTypeSpec());
rootNode = negateNode;
}
token = currentToken();
tokenType = token.getType();
// Loop over additive operators.
while (ADD_OPS.contains(tokenType)) {
TokenType operator = tokenType;
// Create a new operator node and adopt the current tree as its first child.
ICodeNodeType nodeType = ADD_OPS_OPS_MAP.get(operator);
ICodeNode opNode = ICodeFactory.createICodeNode(nodeType);
opNode.addChild(rootNode);
token = nextToken(); // consume the operator
// Parse another term.
// The operator node adopts the term's tree as its second child.
ICodeNode termNode = parseTerm(token);
opNode.addChild(termNode);
TypeSpec termType = termNode != null ? termNode.getTypeSpec() : Predefined.undefinedType;
// The operator node becomes the new root node.
rootNode = opNode;
switch ((PascalTokenType) operator) {
case PLUS:
case MINUS:
{
// Both operands integer => integer result.
if (TypeChecker.areBothInteger(resultType, termType))
resultType = Predefined.integerType;
// Both real operands or one real and one integer operand => real result.
else if (TypeChecker.isAtLeastOneReal(resultType, termType))
resultType = Predefined.realType;
else errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
break;
}
case OR:
{
// Both operands boolean ==> boolean result.
if (TypeChecker.areBothBoolean(resultType, termType))
resultType = Predefined.booleanType;
else errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
break;
}
}
rootNode.setTypeSpec(resultType);
token = currentToken();
tokenType = token.getType();
}
return rootNode;
}
