uCalc API Version: 2.1.3-preview.2 Released: 6/17/2026

Warning

uCalc API Preview Release Notice:The documentation describes the intended behavior of the API. The current preview build contains incomplete features, unoptimized performance, and is subject to breaking changes.

ArgStr

Method

Product: 

Fast Math Parser

Class: 

Callback

Retrieves an argument passed to a callback function, automatically converting its value to a string.

Syntax

ArgStr(int)

Parameters

index
int
The 1-based index of the argument to retrieve. For example, the first argument is at index 1.

Return

string

The string representation of the requested argument's value.

Remarks

The ArgStr method retrieves an argument passed to a callback function as a string. Its key feature is automatic type conversion: if the original argument is a number, boolean, or another type, ArgStr will automatically convert its value to a string representation before returning it.

This simplifies callback logic significantly, as you do not need to check the argument's type and perform manual conversions. It is the most versatile of the Arg functions for retrieving display-ready values.

ArgStr is typically used within a callback that is registered with DefineFunction or DefineOperator.

⚖️ Comparative Analysis

  • vs. Native Delegates (C#) / Function Pointers (C++): In native code, callback arguments have fixed types. To get a string from an integer, you must manually call a conversion function (e.g., ToString(), std::to_string). uCalc's ArgStr handles this conversion implicitly, making the callback code cleaner and more focused on logic rather than type marshalling.

  • vs. Other Arg Methods: While methods like ArgDbl or ArgInt32 are more efficient for direct numeric calculations, ArgStr is the ideal choice when the ultimate goal is to build, format, or display a string.

Examples

Returning a string (from a callback)
				
					using uCalcSoftware;

var uc = new uCalc();

static void TwiceStr(uCalc.Callback cb) {
   cb.ReturnStr(cb.ArgStr(1) + cb.ArgStr(1));
}

uc.DefineFunction("Twice(Txt As String) As String", TwiceStr);
Console.WriteLine(uc.EvalStr("Twice('Bye')"));
				
			
ByeBye
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

void ucalc_call TwiceStr(uCalcBase::Callback cb) {
   cb.ReturnStr(cb.ArgStr(1) + cb.ArgStr(1));
}
int main() {
   uCalc uc;
   uc.DefineFunction("Twice(Txt As String) As String", TwiceStr);
   cout << uc.EvalStr("Twice('Bye')") << endl;
}
				
			
ByeBye
				
					Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub TwiceStr(ByVal cb As uCalc.Callback)
      cb.ReturnStr(cb.ArgStr(1) + cb.ArgStr(1))
   End Sub
   Public Sub Main()
      Dim uc As New uCalc()
      uc.DefineFunction("Twice(Txt As String) As String", AddressOf TwiceStr)
      Console.WriteLine(uc.EvalStr("Twice('Bye')"))
   End Sub
End Module
				
			
ByeBye
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