///FUNCTION: FUNCTION_NAME '(' FUNC_ARGS ')'
private bool TryParseFunction(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($"Undefined Identifier {token.Value} at position {token.Position}");
}
if (stEntry.Type == SymbolTableEntry.EntryType.Function)
{
node = new FunctionASTNode(Accept( ));
Expect(Token.TokenType.OpenParen);
Accept( );
if (TryParseFuncArgs(out var arguments))
{
(node as FunctionASTNode).ArgumentNodes.AddRange(arguments);
}
Expect(Token.TokenType.CloseParen);
Accept( );
}
}
return(node != null);
}
protected double Evaluate(FunctionASTNode node)
{
var entry = _symbolTable.Get(node.Name);
if (entry == null || entry.Type != SymbolTableEntry.EntryType.Function)
{
throw new Exception($"Error Evaluating Expression. Function {node.Name}");
}
return
(( double )
(entry as FunctionSystemTableEntry)
.MethodInfo
.Invoke(null, node.ArgumentNodes.Select(arg => Evaluate(arg as dynamic)).ToArray( )));
}