A practical example of `ByRef` to create a classic `Swap` function that modifies its arguments in the caller's scope.

ID: 1248

See: Advanced Argument Passing 
				
					using uCalcSoftware;

var uc = new uCalc();

static void SwapValues(uCalc.Callback cb) {
   // Get the item handles for the two variables passed by reference
   var item1 = cb.ArgItem(1);
   var item2 = cb.ArgItem(2);

   // Use the item's DataType object to perform a highly efficient, pointer-based swap
   item1.DataType.SwapScalarValues(item1.ValueAddr(), item2.ValueAddr());
}

// Define the Swap function with ByRef parameters
uc.DefineFunction("Swap(ByHandle a, ByHandle b)", SwapValues);

// Define the variables to be swapped
uc.DefineVariable("x = 100");
uc.DefineVariable("y = 200");

Console.WriteLine($"Before: x = {uc.Eval("x")}, y = {uc.Eval("y")}");

// Call the swap function
uc.Eval("Swap(x, y)");

Console.WriteLine($"After:  x = {uc.Eval("x")}, y = {uc.Eval("y")}");
				
			
Before: x = 100, y = 200
After:  x = 200, y = 100
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

void ucalc_call SwapValues(uCalcBase::Callback cb) {
   // Get the item handles for the two variables passed by reference
   auto item1 = cb.ArgItem(1);
   auto item2 = cb.ArgItem(2);

   // Use the item's DataType object to perform a highly efficient, pointer-based swap
   item1.DataType().SwapScalarValues(item1.ValueAddr(), item2.ValueAddr());
}
int main() {
   uCalc uc;
   // Define the Swap function with ByRef parameters
   uc.DefineFunction("Swap(ByHandle a, ByHandle b)", SwapValues);

   // Define the variables to be swapped
   uc.DefineVariable("x = 100");
   uc.DefineVariable("y = 200");

   cout << "Before: x = " << uc.Eval("x") << ", y = " << uc.Eval("y") << endl;

   // Call the swap function
   uc.Eval("Swap(x, y)");

   cout << "After:  x = " << uc.Eval("x") << ", y = " << uc.Eval("y") << endl;
}
				
			
Before: x = 100, y = 200
After:  x = 200, y = 100
Explore 600+ other examples
				
					Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub SwapValues(ByVal cb As uCalc.Callback)
      '// Get the item handles for the two variables passed by reference
      Dim item1 = cb.ArgItem(1)
      Dim item2 = cb.ArgItem(2)
      
      '// Use the item's DataType object to perform a highly efficient, pointer-based swap
      item1.DataType.SwapScalarValues(item1.ValueAddr(), item2.ValueAddr())
   End Sub
   Public Sub Main()
      Dim uc As New uCalc()
      '// Define the Swap function with ByRef parameters
      uc.DefineFunction("Swap(ByHandle a, ByHandle b)", AddressOf SwapValues)
      
      '// Define the variables to be swapped
      uc.DefineVariable("x = 100")
      uc.DefineVariable("y = 200")
      
      Console.WriteLine($"Before: x = {uc.Eval("x")}, y = {uc.Eval("y")}")
      
      '// Call the swap function
      uc.Eval("Swap(x, y)")
      
      Console.WriteLine($"After:  x = {uc.Eval("x")}, y = {uc.Eval("y")}")
   End Sub
End Module
				
			
Before: x = 100, y = 200
After:  x = 200, y = 100
Explore 600+ other examples