private bool TryParseFunction(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($"Undefined identifier {token.Value} at position {token.Position}");
}
if (stEntry.Type == EntryType.Function)
{
node = new FunctionIdentifierAstNode(Accept());
Expect(TokenType.OpenParen);
Accept();
if (TryParseFuncArgs(out var args))
{
(node as FunctionIdentifierAstNode).ArgumentNodes.AddRange(args);
}
Expect(TokenType.CloseParen);
Accept();
}
}
return(node != null);
}
private double Evaluate(FunctionIdentifierAstNode node)
{
var entry = _symbolTable.Get(node.Name);
if (entry is null || entry.Type != EntryType.Function)
{
throw new Exception($"Error evaluating expression. Function {node.Name}");
}
return
((double)
(entry as FunctionSymbolTableEntry)
.MethodInfo
.Invoke(null, node.ArgumentNodes.Select(arg => Evaluate(arg as dynamic)).ToArray()));
}
