private double Evaluate(VariableIdentifierAstNode node)
{
var entry = _symbolTable.Get(node.Name);
if (entry is null || entry.Type != EntryType.Variable)
{
throw new Exception($"Error evaluating expression. Variable {node.Name}");
}
return((entry as VariableSymbolTableEntry).Value);
}
private bool TryParseVariable(out AstNode node)
{
node = null;
if (IsNext(TokenType.Identifier))
{
var token = _lexer.Peek();
var stEntry = _symbolTable.Get(token.Value);
if (stEntry is null)
{
throw new Exception($"Undefined identifier {token.Value} at position {token.Position}");
}
if (stEntry.Type == EntryType.Variable)
{
node = new VariableIdentifierAstNode(Accept());
}
}
return(node != null);
}
