private AstNode Factor()
{
// FACTOR = UNARY-OP FACTOR |
// INCREMENT-BY-ONE VARIABLE |
// DECREMENT-BY-ONE VARIABLE |
// NUMBER (INCREMENT-BY-ONE) |
// NUMBER (DECREMENT-BY-ONE) |
// STRING | CHAR | BOOLEAN |
// PARAM-START EXPRESSION PARAM-END |
// VARIABLE
var token = _currentToken;
if (Tokens.IsUnaryOperator(token.Type))
{
Eat(token.Type); return(new UnaryOperationNode(token, Factor()));
}
else if (token.Type == Tokens.IncrementByOne)
{
Eat(token.Type); return(new PreIncrementNode(Variable()));
}
else if (token.Type == Tokens.DecrementByOne)
{
Eat(token.Type); return(new PreDecrementNode(Variable()));
}
else if (Tokens.IsNumberType(token.Type))
{
return(Number());
}
else if (token.Type == Tokens.String)
{
Eat(token.Type); return(new StringNode((string)token.Value));
}
else if (token.Type == Tokens.Character)
{
Eat(token.Type); return(new CharacterNode((char)token.Value));
}
else if (token.Type == Tokens.True)
{
Eat(token.Type); return(new BooleanNode(true));
}
else if (token.Type == Tokens.False)
{
Eat(token.Type); return(new BooleanNode(false));
}
else if (token.Type == Tokens.ParamStart)
{
Eat(Tokens.ParamStart);
var expression = Expression();
Eat(Tokens.ParamEnd);
return(expression);
}
else
{
var variable = Variable();
if (token.Type == Tokens.IncrementByOne)
{
Eat(token.Type); return(new PostIncrementNode(variable));
}
else if (token.Type == Tokens.DecrementByOne)
{
Eat(token.Type); return(new PostDecrementNode(variable));
}
return(variable);
}
throw new Exception("Factor bad. Very bad. No like it. Stop.");
}
private AstNode Statement()
{
// STATEMENT = BLOCK |
// var VARIABLE-DECL | // implicit variable declaration
// IDENITIFER VARIABLE-DECL | // explicit variable declaration with user-defined type
// TYPE-SPEC VARAIBLE-DECL | // explicit variable declaration with primitive type
// IDENTIFIER ASSIGNMENT |
// IDENTIFIER INCREMENT-BY EXPRESSION |
// IDENTIFIER DECREMENT-BY EXPRESSION |
// IDENTIFIER MULTIPLY-BY EXPRESSION |
// IDENTIFIER DIVIDE-BY EXPRESSION |
// RETURN EXPRESSION |
// BRANCH |
// NO-OP
if (_currentToken.Type == Tokens.BlockStart)
{
return(Block());
}
else if (_currentToken.Type == Tokens.Variable)
{
Eat(_currentToken.Type);
return(VariableDeclaration(TypeNode.Inferred));
}
else if (_currentToken.Type == Tokens.Identifier)
{
var id = _currentToken.Value.ToString();
Eat(Tokens.Identifier);
if (_currentToken.Type == Tokens.Assign)
{
return(Assignment(new VariableNode(id)));
}
else if (_currentToken.Type == Tokens.Identifier)
{
return(VariableDeclaration(new TypeNode(id)));
}
else if (_currentToken.Type == Tokens.IncrementBy)
{
Eat(Tokens.IncrementBy);
return(new IncrementByNode(new VariableNode(id), Expression()));
}
else if (_currentToken.Type == Tokens.DecrementBy)
{
Eat(Tokens.DecrementBy);
return(new DecrementByNode(new VariableNode(id), Expression()));
}
else if (_currentToken.Type == Tokens.MultiplyBy)
{
Eat(Tokens.MultiplyBy);
return(new MultiplyByNode(new VariableNode(id), Expression()));
}
else if (_currentToken.Type == Tokens.DivideBy)
{
Eat(Tokens.DivideBy);
return(new DivideByNode(new VariableNode(id), Expression()));
}
}
else if (Tokens.IsPrimitiveType(_currentToken.Type))
{
return(VariableDeclaration(TypeSpec()));
}
else if (_currentToken.Type == Tokens.Return)
{
Eat(Tokens.Return);
return(new ReturnNode(Expression()));
}
else if (_currentToken.Type == Tokens.Branch)
{
Eat(Tokens.Branch);
return(Branch());
}
else
{
return(new NoOpNode());
}
throw new Exception("bad statement");
}