I decided to change the Call Instruction to the one below. As we return with an event code we consume the NIX and process the first “On” that will test for event code and continue to next “On” if not.

At this point I can consider dropping “On” and replace it with “If” or “Switch” – one lesst instruction to worry about. But, I will consider that as all instructions are drafted.

I really like this version of Call as it leaves me with a minimal function call if I don’t need On. Let’s test it out:

Func MyFunc(uint32 x)
    if( x = 1)
         Raise E1("Text 1")
    elseif(x=2)
         Raise E2(2)
    else
         Raise Error(x, "X is wrong value")
    end
Event E1(string s)
Event E2(uint32 i)
Event Error(uint32 i, string text)
End

uint32 x

for x=1 to 3
    Call MyFunc(1)
    On E1(string s)
        println("Event E1 is called")
    On E2(uint32 i)
        println("Event E2 is called")
    On Error(uint32 i, string text)
        println("Error is called")
    End
End

The annotaded figure below show hoe Call would be in this example. I will return to details about On Instructions later.The key with Event’s is that unless it is handled we do nothing, we just fall through. The function will mark Event’s as Optional, Mandatory or Static. If we must have a On we mark it as Mandatory etc.

All the Plain entries in here have served their design purpose as I consolidate and wrap up Plain Specification. I usually never bother with a specification on software I do at home, but the complexity and technical design of both language and VM have to many details that needs to be right.

The new VM Instruction header is simplified as shown above.

The old “Object Descriptor” used for parameters have been replaced with a “Data Descriptor”.

The Expression Tables have been moved out from the Instruction and attacched as separate tables at the end of the Instruction Table.

The VM core will be modified, I will return to this later. The main difference is in the Data Descriptor, but also all the details that now get nailed down right so we can move on.

At the end I probably also need to clean up this blog my marking old Plain discussions as obsolete. This happens in engineering as you move forward improving designs.