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.

ArgCount

Method

Product: 

Fast Math Parser

Class: 

Callback

Gets the number of arguments passed to the current callback function, essential for creating variadic functions.

Syntax

ArgCount()

Parameters

[None]

Return

int

The total number of arguments passed to the callback. Returns 0 if the function was called with no arguments.

Remarks

The ArgCount method returns the total number of arguments passed to a callback function. It is the primary tool for creating variadic functions—functions that can accept a variable number of arguments.

This method can only be called from within a callback context, typically one registered via DefineFunction or DefineOperator. It is commonly used as the upper bound for a loop that iterates through the provided arguments.

csharp

static void MySum(uCalc.Callback cb) {
double total = 0;
// Use ArgCount() to determine how many times to loop.
for (int i = 1; i <= cb.ArgCount(); i++) {
total = total + cb.Arg(i);
}
cb.Return(total);
}

// The '...' syntax marks this as a variadic function.
uc.DefineFunction("Sum(...)", MySum);
Console.WriteLine(uc.Eval("Sum(10, 20, 30)")); // Outputs 60

💡 Comparative Analysis

Most modern languages have a mechanism for variadic functions, but uCalc's integration with its dynamic expression engine is unique.

  • vs. C# params / C++ ...: In compiled languages, variadic functions are a compile-time feature. The function signature is fixed in code.

    // C# Examplepublic double Sum(params double[] numbers) { ... }

    uCalc's advantage is its runtime dynamism. A user can define a variadic function within a string expression that is evaluated at runtime, providing a level of flexibility impossible in pre-compiled code. The ArgCount method is the key that unlocks this capability within the callback's logic.

  • vs. JavaScript ...args: While JavaScript's rest parameters (...args) are also dynamic, uCalc's ArgCount and its companion methods (Arg, ArgItem, etc.) provide a more structured and type-aware API for inspecting arguments from within a strongly-typed host environment (like C# or C++), which is a distinct advantage over loosely-typed scripting.

Examples

Defining a callback function with a variable number of arguments

ID: 12

See: (Constructor), Arg, ArgCount, DefineFunction, Introduction, Return 
				
					using uCalcSoftware;

var uc = new uCalc();

static void MyAverage(uCalc.Callback cb) {
   double Total = 0;
   for (int x = 1; x <= cb.ArgCount(); x++) {
      Total = Total + cb.Arg(x);
   }
   cb.Return(Total / cb.ArgCount());
}

uc.DefineFunction("Average(x ...)", MyAverage);
Console.WriteLine(uc.Eval("Average(10, 3, 7, 4)"));
				
			
6
Explore 600+ other examples
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

void ucalc_call MyAverage(uCalcBase::Callback cb) {
   double Total = 0;
   for (int x = 1; x <= cb.ArgCount(); x++) {
      Total = Total + cb.Arg(x);
   }
   cb.Return(Total / cb.ArgCount());
}
int main() {
   uCalc uc;
   uc.DefineFunction("Average(x ...)", MyAverage);
   cout << uc.Eval("Average(10, 3, 7, 4)") << endl;
}
				
			
6
Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub MyAverage(ByVal cb As uCalc.Callback)
      Dim Total As Double = 0
      For x  As Integer = 1 To cb.ArgCount()
         Total = Total + cb.Arg(x)
      Next
      cb.Return(Total / cb.ArgCount())
   End Sub
   Public Sub Main()
      Dim uc As New uCalc()
      uc.DefineFunction("Average(x ...)", AddressOf MyAverage)
      Console.WriteLine(uc.Eval("Average(10, 3, 7, 4)"))
   End Sub
End Module
				
			
6
Explore 600+ other examples
Passing arg ByHandle to retrieve meta data such as arg data type; and AnyType

ID: 13

See: ArgCount, ArgItem, DataType = [DataType], DefineFunction, Name = [string], ValueStr 
				
					using uCalcSoftware;

var uc = new uCalc();

static void DisplayArgs(uCalc.Callback cb) {
   for (int x = 1; x <= cb.ArgCount(); x++) {
      Console.WriteLine(cb.ArgItem(x).ValueStr() + "  Type: " + cb.ArgItem(x).DataType.Name);
   }
}

uc.DefineFunction("DisplayArgs(ByHandle Arg As AnyType ...)", DisplayArgs);
uc.Eval("DisplayArgs(5, 3+2*#i, 'Hello', True, False, Int16(5+4.1))");
				
			
5  Type: double
3+2i  Type: complex
Hello  Type: string
true  Type: bool
false  Type: bool
9  Type: int16
Explore 600+ other examples
				
					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

void ucalc_call DisplayArgs(uCalcBase::Callback cb) {
   for (int x = 1; x <= cb.ArgCount(); x++) {
      cout << cb.ArgItem(x).ValueStr() + "  Type: " + cb.ArgItem(x).DataType().Name() << endl;
   }
}
int main() {
   uCalc uc;
   uc.DefineFunction("DisplayArgs(ByHandle Arg As AnyType ...)", DisplayArgs);
   uc.Eval("DisplayArgs(5, 3+2*#i, 'Hello', True, False, Int16(5+4.1))");
}
				
			
5  Type: double
3+2i  Type: complex
Hello  Type: string
true  Type: bool
false  Type: bool
9  Type: int16
Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub DisplayArgs(ByVal cb As uCalc.Callback)
      For x  As Integer = 1 To cb.ArgCount()
         Console.WriteLine(cb.ArgItem(x).ValueStr() + "  Type: " + cb.ArgItem(x).DataType.Name)
      Next
   End Sub
   Public Sub Main()
      Dim uc As New uCalc()
      uc.DefineFunction("DisplayArgs(ByHandle Arg As AnyType ...)", AddressOf DisplayArgs)
      uc.Eval("DisplayArgs(5, 3+2*#i, 'Hello', True, False, Int16(5+4.1))")
   End Sub
End Module
				
			
5  Type: double
3+2i  Type: complex
Hello  Type: string
true  Type: bool
false  Type: bool
9  Type: int16
Explore 600+ other examples