private Node VariableDeclaration()
{
bool local = false;
if (LookAhead(1) == TokenType.VAR)
{
Match(TokenType.VAR);
local = true;
}
Node result = Variable();
if (LookAhead(1) == TokenType.ASSIGN)
{
SourcePosition pos = Match(TokenType.ASSIGN).Position;
Node value = Expression();
result = new AssignNode(pos, result, value, local);
}
if (LookAhead(1) == TokenType.END_STATEMENT)
{
Match(TokenType.END_STATEMENT);
}
return result;
}
private Node SumExpression()
{
// term ((PLUS^|MINUS^) term)*
Node termExpression = Term();
TokenType next = LookAhead(1);
if (LookAhead(2) != TokenType.STRING_LITERAL)
{
while (next == TokenType.PLUS ||
next == TokenType.PLUS_PLUS ||
next == TokenType.PLUS_ASSIGN ||
next == TokenType.MINUS ||
next == TokenType.MINUS_MINUS ||
next == TokenType.MINUS_ASSIGN)
{
if (next == TokenType.PLUS)
{
termExpression = new AddOpNode(Match(TokenType.PLUS).Position, termExpression, Term());
}
else if (next == TokenType.PLUS_PLUS)
{
Node increment = new IntegerNode(Match(TokenType.PLUS_PLUS).Position, 1);
Node addNode = new AddOpNode(increment.Position, termExpression, increment);
termExpression = new AssignNode(termExpression.Position, termExpression, addNode, false);
}
else if (next == TokenType.PLUS_ASSIGN)
{
Token plusAssign = Match(TokenType.PLUS_ASSIGN);
Node increment = Expression();
Node addNode = new AddOpNode(plusAssign.Position, termExpression, increment);
termExpression =
new AssignNode(termExpression.Position, termExpression, addNode, false);
}
else if (next == TokenType.MINUS)
{
termExpression =
new SubtractOpNode(Match(TokenType.MINUS).Position, termExpression, Term());
}
else if (next == TokenType.MINUS_MINUS)
{
Node deincrement = new IntegerNode(Match(TokenType.MINUS_MINUS).Position, 1);
Node subtractNode = new SubtractOpNode(deincrement.Position, termExpression, deincrement);
termExpression =
new AssignNode(termExpression.Position, termExpression, subtractNode, false);
}
else if (next == TokenType.MINUS_ASSIGN)
{
Token minusAssign = Match(TokenType.MINUS_ASSIGN);
Node deincrement = Expression();
Node subtractNode = new SubtractOpNode(minusAssign.Position, termExpression, deincrement);
termExpression =
new AssignNode(termExpression.Position, termExpression, subtractNode, false);
}
next = LookAhead(1);
}
}
return termExpression;
}