private bool TryParseIdentifier(out ASTNode node)
{
node = null;
if (IsNext(Token.TokenType.Identifier))
{
var token = Accept();
var stEntry = _symbolTable.Get(token.Value);
if (stEntry == null)
{
throw new Exception($"Undefined Identifier {token.Value} at position {token.Position}");
}
if (stEntry.Type == SymbolTableEntry.EntryType.Variable)
{
node = new VariableIdentifierASTNode(token, token.Value);
}
else
{
//TODO: Handle Functions next
}
}
return(node != null);
}
protected double Evaluate(VariableIdentifierASTNode node)
{
var entry = _symbolTable.Get(node.Name);
if (entry == null || entry.Type != SymbolTableEntry.EntryType.Variable)
{
throw new Exception($"Error Evaluating Expression. Variable {node.Name}");
}
return((entry as VariableSymbolTableEntry).Value);
}
private bool TryParseVariable(out ASTNode node)
{
node = null;
if (IsNext(Token.TokenType.Identifier))
{
var token = _lexer.Peek();
var stEntry = _symbolTable.Get(token.Value);
if (stEntry == null)
{
throw new Exception($"Undefined Identifier {token.Value} at position {token.Position}");
}
if (stEntry.Type == SymbolTableEntry.EntryType.Variable)
{
node = new VariableIdentifierASTNode(Accept( ));
}
}
return(node != null);
}
