uCalc API Version: 5.7.0-preview.1 Released: 7/30/2026

Warning

uCalc API Preview Release Notice:This preview documentation describes the intended behavior of the API. It is not fully accurate or complete.The current preview build contains incomplete features, unoptimized performance, and is subject to breaking changes.Use of the preview version in your production code is not recommended.

ErrorHandlerResponse

Enum

Product: 

Class: 

Error hander responses

Name ▲ ▼ Value ▲ ▼ Description ▲ ▼
Abort

Immediately stops parsing
Resume

Continues parsing or evaluating (after the handler resolves the error)
ReRaise

Raises the same error again for the next uCalc error handler to take care of

Remarks

Use this to set the option for [topic: uCalc.ErrorResponse].

It is also the return value of [topic: uCalc.Callback.ErrorRaise] and [topic: uCalc.Callback.ErrorRaiseMessage]

Examples

A practical example of a proactive error handler that automatically defines undeclared variables on the fly, allowing the expression to successfully resume execution.

ID: 1190

See: AddHandler, Error = [ErrorInfo], Error handling and control flow, ErrorCode, ErrorHandlerResponse, Handling Errors, Response = [ErrorHandlerResponse] 
				
					using uCalcSoftware;

var uc = new uCalc();

// This handler automatically defines variables when they are first used.
static void AutoDefineHandler(Handle_uCalc h) {
   var uc = new uCalc(h);
   // Check if the error is specifically an undefined identifier
   if (uc.Error.Code == ErrorCode.Undefined_Identifier) {
      Console.WriteLine($"Handler: '{uc.Error.Symbol}' is undefined. Defining it now.");
      uc.DefineVariable(uc.Error.Symbol);

      // Tell the engine to resume the operation
      uc.Error.Response = ErrorHandlerResponse.Resume;
   }
}


uc.Error.AddHandler(AutoDefineHandler);

// 'my_var' doesn't exist yet, but the handler will create it.
var result = uc.EvalStr("my_var = 100; my_var = my_var * 2");

Console.WriteLine($"Final result: {result}");
				
			
Handler: 'my_var' is undefined. Defining it now.
Final result: 200
Explore 600+ other examples
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

// This handler automatically defines variables when they are first used.
void ucalc_call AutoDefineHandler(Handle_uCalc h) {
   auto uc = uCalc(h);
   // Check if the error is specifically an undefined identifier
   if (uc.Error().Code() == ErrorCode::Undefined_Identifier) {
      cout << "Handler: '" << uc.Error().Symbol() << "' is undefined. Defining it now." << endl;
      uc.DefineVariable(uc.Error().Symbol());

      // Tell the engine to resume the operation
      uc.Error().Response(ErrorHandlerResponse::Resume);
   }
}

int main() {
   uCalc uc;
   uc.Error().AddHandler(AutoDefineHandler);

   // 'my_var' doesn't exist yet, but the handler will create it.
   auto result = uc.EvalStr("my_var = 100; my_var = my_var * 2");

   cout << "Final result: " << result << endl;
}
				
			
Handler: 'my_var' is undefined. Defining it now.
Final result: 200
Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   
   '// This handler automatically defines variables when they are first used.
   Public Sub AutoDefineHandler(ByVal h As Handle_uCalc)
      Dim uc As New uCalc(h)
      '// Check if the error is specifically an undefined identifier
      If uc.Error.Code = ErrorCode.Undefined_Identifier Then
         Console.WriteLine($"Handler: '{uc.Error.Symbol}' is undefined. Defining it now.")
         uc.DefineVariable(uc.Error.Symbol)
         
         '// Tell the engine to resume the operation
         uc.Error.Response = ErrorHandlerResponse.Resume
      End If
   End Sub
   
   Public Sub Main()
      Dim uc As New uCalc()
      uc.Error.AddHandler(AddressOf AutoDefineHandler)
      
      '// 'my_var' doesn't exist yet, but the handler will create it.
      Dim result = uc.EvalStr("my_var = 100; my_var = my_var * 2")
      
      Console.WriteLine($"Final result: {result}")
   End Sub
End Module
				
			
Handler: 'my_var' is undefined. Defining it now.
Final result: 200
Explore 600+ other examples