Creates a custom `IIf` function to demonstrate basic lazy evaluation. The division-by-zero error in the unevaluated branch is safely ignored.

ID: 1229

See: Lazy Evaluation (ByExpr) 
				
					using uCalcSoftware;

var uc = new uCalc();

static void MyIIf(uCalc.Callback cb) {
   var condition = cb.ArgBool(1);
   var thenPart = cb.ArgExpr(2);
   var elsePart = cb.ArgExpr(3);

   if (condition) {
      cb.Return(thenPart.Evaluate());
   } else {
      cb.Return(elsePart.Evaluate());
   }
}

uc.DefineFunction("MyIIf(cond As Bool, ByExpr thenExpr, ByExpr elseExpr)", MyIIf);

// The 'else' branch contains 1/0, but since the condition is true,
// it is never evaluated.
Console.WriteLine(uc.Eval("MyIIf(10 > 5, 100, 1/0)"));

// The 'then' branch contains 1/0, but it is never evaluated.
Console.WriteLine(uc.Eval("MyIIf(10 < 5, 1/0, 200)"));
				
			
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					#include <iostream>
#include "uCalc.h"

using namespace std;
using namespace uCalcSoftware;

void ucalc_call MyIIf(uCalcBase::Callback cb) {
   auto condition = cb.ArgBool(1);
   auto thenPart = cb.ArgExpr(2);
   auto elsePart = cb.ArgExpr(3);

   if (condition) {
      cb.Return(thenPart.Evaluate());
   } else {
      cb.Return(elsePart.Evaluate());
   }
}
int main() {
   uCalc uc;
   uc.DefineFunction("MyIIf(cond As Bool, ByExpr thenExpr, ByExpr elseExpr)", MyIIf);

   // The 'else' branch contains 1/0, but since the condition is true,
   // it is never evaluated.
   cout << uc.Eval("MyIIf(10 > 5, 100, 1/0)") << endl;

   // The 'then' branch contains 1/0, but it is never evaluated.
   cout << uc.Eval("MyIIf(10 < 5, 1/0, 200)") << endl;
}
				
			
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					Imports System
Imports uCalcSoftware
Public Module Program
   
   Public Sub MyIIf(ByVal cb As uCalc.Callback)
      Dim condition = cb.ArgBool(1)
      Dim thenPart = cb.ArgExpr(2)
      Dim elsePart = cb.ArgExpr(3)
      
      If condition Then
         cb.Return(thenPart.Evaluate())
      Else
         cb.Return(elsePart.Evaluate())
      End If
   End Sub
   Public Sub Main()
      Dim uc As New uCalc()
      uc.DefineFunction("MyIIf(cond As Bool, ByExpr thenExpr, ByExpr elseExpr)", AddressOf MyIIf)
      
      '// The 'else' branch contains 1/0, but since the condition is true,
      '// it is never evaluated.
      Console.WriteLine(uc.Eval("MyIIf(10 > 5, 100, 1/0)"))
      
      '// The 'then' branch contains 1/0, but it is never evaluated.
      Console.WriteLine(uc.Eval("MyIIf(10 < 5, 1/0, 200)"))
   End Sub
End Module
				
			
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