Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub MyFunc(ByVal cb As uCalc.Callback)
      '// This error occurs during evaluation, not parsing.
      cb.Error.Raise("Manual evaluation failure!")
   End Sub
   
   Public Sub MyHandler(ByVal h As Handle_uCalc)
      Dim uc As New uCalc(h)
      Console.WriteLine($"Handler triggered for error: {uc.Error.Message}")
      Console.WriteLine($"ErrorExpression() returned: '{uc.Error.Expression}'")
      Console.WriteLine($"Is expression empty? {uc.Error.Expression = ""}")
   End Sub
   
   Public Sub Main()
      Dim uc As New uCalc()
      uc.DefineFunction("MyFunc()", AddressOf MyFunc)
      uc.Error.AddHandler(AddressOf MyHandler)
      
      '// The expression 'MyFunc()' itself is valid syntactically.
      Console.WriteLine(uc.EvalStr("MyFunc()"))
   End Sub
End Module