Example 2a

In Example 2, the argument to CTOR, the constructor for the Primitives class, was defined to be Int32. This means that the .NET Framework will allow a client to specify any integer when it creates an instance of the Primitives class. What happens if the client uses a parameter of 2? Clearly this is going to cause an APL DOMAIN ERROR when used to set ⎕IO.

To investigate this case, change the line of code in program.cs that creates an instance of the Primitives class, passing the argument 2, like this: 

                  Primitives apl = new Primitives(2);

aplclasses2a_1
Figure 1: aplclasses2a_1

Then click Debug/Start Without debugging (or press Ctrl+F5) to run the program.

… as we have built the Dyalog .NET class to use the Development DLL, the APL Session appears, and the Tracer can be used to debug the problem. You can see that the constructor CTOR has stopped with a DOMAIN ERROR. Meanwhile, the C# program is still waiting for the call (to create an instance of Primitives) to finish.

aplclasses2a_2
Figure 2: aplclasses2a_2

Notice that in Dyalog, the )SI System Command provides information about the entire calling stack, including the .NET function calls that are involved. Notice too that the CTOR function, the constructor for this APL .NET class, is running here in APL thread 1, which is associated with the system thread 30732.

In this case, debugging is simple, and you can simply type: 

      IO←1
      →⎕LC

Now, the CTOR function completes, the program continues and the output is displayed.

aplclasses2a_3
Figure 3: aplclasses2a_3