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.

(Constructor)

Constructor

Product: 

Fast Math Parser

Class: 

Callback

uCalc.Callback constructor

Remarks

Callbacks object are not meant to be explicitly constructed. Instead it is passed as an argument for a callback function.

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)"));
				
			
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					#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;
}
				
			
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					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
				
			
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Passing arg ByExpr (delayed lazy eval) and ByHandle

ID: 14

See: (Constructor), Arg, ArgExpr, ArgItem, DefineFunction, Evaluate, Introduction, Value(double) 
				
					using uCalcSoftware;

var uc = new uCalc();

static void MySum(uCalc.Callback cb) {
   var Total = 0.0;
   var Expr = cb.ArgExpr(1);
   var Start = cb.Arg(2);
   var Finish = cb.Arg(3);
   var Variable = cb.ArgItem(4);

   for (double x = Start; x <= Finish; x++) {
      Variable.Value(x);
      Total += Expr.Evaluate();
   }
   cb.Return(Total);
}

uc.DefineVariable("x");
uc.DefineFunction("Sum(ByExpr Expr, Start, Finish, ByHandle Var)", MySum);
Console.WriteLine(uc.Eval("Sum(x ^ 2, 1, 10, x)"));

				
			
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

void ucalc_call MySum(uCalcBase::Callback cb) {
   auto Total = 0.0;
   auto Expr = cb.ArgExpr(1);
   auto Start = cb.Arg(2);
   auto Finish = cb.Arg(3);
   auto Variable = cb.ArgItem(4);

   for (double x = Start; x <= Finish; x++) {
      Variable.Value(x);
      Total += Expr.Evaluate();
   }
   cb.Return(Total);
}
int main() {
   uCalc uc;
   uc.DefineVariable("x");
   uc.DefineFunction("Sum(ByExpr Expr, Start, Finish, ByHandle Var)", MySum);
   cout << uc.Eval("Sum(x ^ 2, 1, 10, x)") << endl;

}
				
			
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					Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub MySum(ByVal cb As uCalc.Callback)
      Dim Total = 0.0
      Dim Expr = cb.ArgExpr(1)
      Dim Start = cb.Arg(2)
      Dim Finish = cb.Arg(3)
      Dim Variable = cb.ArgItem(4)
      
      For x  As Double = Start To Finish
         Variable.Value(x)
         Total += Expr.Evaluate()
      Next
      cb.Return(Total)
   End Sub
   Public Sub Main()
      Dim uc As New uCalc()
      uc.DefineVariable("x")
      uc.DefineFunction("Sum(ByExpr Expr, Start, Finish, ByHandle Var)", AddressOf MySum)
      Console.WriteLine(uc.Eval("Sum(x ^ 2, 1, 10, x)"))
      
   End Sub
End Module
				
			
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