A practical example of `ByHandle` to create a `TypeOf` function that introspects an argument and returns its data type name as a string.

ID: 1250

See: Advanced Argument Passing 
				
					using uCalcSoftware;

var uc = new uCalc();

static void GetTypeOf(uCalc.Callback cb) {
   // Get the Item object for the argument
   var item = cb.ArgItem(1);

   // Get the item's DataType, then its name, and return it as a string
   cb.ReturnStr(item.DataType.Name);
}

// The ByHandle modifier passes the argument's metadata (Item) instead of its value
uc.DefineFunction("TypeOf(ByHandle arg As AnyType) As String", GetTypeOf);

uc.DefineVariable("myInt As Int = 10");
uc.DefineVariable("myStr As String = 'hello'");
uc.DefineVariable("myDbl = 3.14"); // Type is inferred as double

Console.WriteLine($"Type of myInt: {uc.EvalStr("TypeOf(myInt)")}");
Console.WriteLine($"Type of myStr: {uc.EvalStr("TypeOf(myStr)")}");
Console.WriteLine($"Type of myDbl: {uc.EvalStr("TypeOf(myDbl)")}");
				
			
Type of myInt: int
Type of myStr: string
Type of myDbl: double
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

void ucalc_call GetTypeOf(uCalcBase::Callback cb) {
   // Get the Item object for the argument
   auto item = cb.ArgItem(1);

   // Get the item's DataType, then its name, and return it as a string
   cb.ReturnStr(item.DataType().Name());
}
int main() {
   uCalc uc;
   // The ByHandle modifier passes the argument's metadata (Item) instead of its value
   uc.DefineFunction("TypeOf(ByHandle arg As AnyType) As String", GetTypeOf);

   uc.DefineVariable("myInt As Int = 10");
   uc.DefineVariable("myStr As String = 'hello'");
   uc.DefineVariable("myDbl = 3.14"); // Type is inferred as double

   cout << "Type of myInt: " << uc.EvalStr("TypeOf(myInt)") << endl;
   cout << "Type of myStr: " << uc.EvalStr("TypeOf(myStr)") << endl;
   cout << "Type of myDbl: " << uc.EvalStr("TypeOf(myDbl)") << endl;
}
				
			
Type of myInt: int
Type of myStr: string
Type of myDbl: double
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					Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub GetTypeOf(ByVal cb As uCalc.Callback)
      '// Get the Item object for the argument
      Dim item = cb.ArgItem(1)
      
      '// Get the item's DataType, then its name, and return it as a string
      cb.ReturnStr(item.DataType.Name)
   End Sub
   Public Sub Main()
      Dim uc As New uCalc()
      '// The ByHandle modifier passes the argument's metadata (Item) instead of its value
      uc.DefineFunction("TypeOf(ByHandle arg As AnyType) As String", AddressOf GetTypeOf)
      
      uc.DefineVariable("myInt As Int = 10")
      uc.DefineVariable("myStr As String = 'hello'")
      uc.DefineVariable("myDbl = 3.14") '// Type is inferred as double
      
      Console.WriteLine($"Type of myInt: {uc.EvalStr("TypeOf(myInt)")}")
      Console.WriteLine($"Type of myStr: {uc.EvalStr("TypeOf(myStr)")}")
      Console.WriteLine($"Type of myDbl: {uc.EvalStr("TypeOf(myDbl)")}")
   End Sub
End Module
				
			
Type of myInt: int
Type of myStr: string
Type of myDbl: double
Explore 600+ other examples