extension method implementation does not work with parameterized input

[ibt1haj]

i have implemented a extension function in ncalc-async like so

public static async Task<object> EvaluateCustomMathFunction(Expression exp)
{
    exp.EvaluateFunctionAsync += NCalcExtensionFunctions;
    var result = await exp.EvaluateAsync();
    return result;
}

private static async Task NCalcExtensionFunctions(string name, FunctionArgs args)
{
    if (name == Constants.Pos)
    {
        var tempResult = await args.Parameters[0].EvaluateAsync();

        if (tempResult is IEnumerable<object> list)
        {
            args.Result = list.Select(x => Convert.ToDouble(x) > 0 ? x : 0);
        }
        else
        {
            var doubleResult = Convert.ToDouble(tempResult);
            args.Result = doubleResult > 0 ? doubleResult : 0;
        }
    }
}

the line

var tempResult = await args.Parameters[0].EvaluateAsync();

always returns zero in case of parameterized input

following is a test case with parameterized input

 [Test]
 public async Task EvaluateCustomMathFunction_WithParameters()
 {
     // Arrange
     var exp = new Expression("Pos(A)", EvaluateOptions.IterateParameters);
     exp.Parameters["A"] = new int[] { 5, 10, -5, 10 };

     // Act
     var result = (IEnumerable) await CustomExpressionEvaluation.EvaluateCustomMathFunction(exp);

     // Assert
     Assert.AreEqual(new int[] { 5, 10, 0, 10 },result);
 }

if the input is a static value then the extension function works correctly

[Test]
public async Task EvaluateCustomMathFunction_PositiveNumber()
{
    // Arrange
    var exp = new Expression("Pos(-5)"); 

    // Act
    var result = await CustomExpressionEvaluation.EvaluateCustomMathFunction(exp);

    // Assert
    Assert.That(result, Is.EqualTo(0)); // The method should return 0 for negative input
}

what am i missing in my implementation of the extension method?
i have also opened a discussion for it on #22

[yallie]

Hello @ibt1haj,

I never used EvaluateOptions.IterateParameters, and it looks to me that IterateParameters implementation is broken.
But I think it's easy to work around this limitation:

private static async Task NCalcExtensionFunctions(string name, FunctionArgs args)
{
	if (name == "Pos")
	{
		var temp = await args.Parameters[0].EvaluateAsync();
		args.Result = Convert.ToDouble(temp) > 0 ? temp : 0;
	}
}

public static async Task<object[]> EvaluateArray(string expression, Dictionary<string, object> parameters)
{
	var expr = new Expression(expression, EvaluateOptions.None);
	expr.EvaluateFunctionAsync += NCalcExtensionFunctions;

	// convert array parameters to scalar parameters
	var count = parameters.Values.OfType<Array>().Min(p => p.Length);
	var results = new List<object>();
	
	for (var i = 0; i < count; i++)
	{
		// get parameters
		foreach (var pair in parameters)
		{
			expr.Parameters[pair.Key] = ((Array)pair.Value).GetValue(i);
		}
		
		// save results
		results.Add(await expr.EvaluateAsync());
	}
	
	return results.ToArray();
}

[yallie]

Here is the full sample code: https://dotnetfiddle.net/fToXRw