Universe Basic Dynamic Array Relative Operation - universe

Question

Universe dynamic array relative operation (using -1) works in a strange way.
Operation below does not add new element in position <1,1,5> as I expected instead adds '1,1,5' to DYNAMIC.ARRAY<1,1,1>.
DYNAMIC.ARRAY = ' '
DYNAMIC.ARRAY<1,-1,5> = '1,1,5' ; *Adds to 1,1,1 not 1,1,5 when DYNAMIC.ARRAY contains only whitespaces before this operation
However same operation works as expected if dynamic array contains non empty value. Final result after executing code below will be DYNAMIC.ARRAY<1,1,1> = '1,1,1' and DYNAMIC.ARRAY<1,2,5> = '1,2,5'.
DYNAMIC.ARRAY = ' '
DYNAMIC.ARRAY<-1> = '1,1,1'
DYNAMIC.ARRAY<1,-1,5> = '1,2,5' ; *Adds to right position 1,2,5 when DYNAMIC.ARRAY is initialised to non empty value before this operation
Is this an expected behaviour in Universe?

Answer 1

When you use -1 it should be on the deepest level of nesting value.
The way multivalued fields work, what you want to do doesn't really make sense.
Say your record is is a reflection of things that customer bought, your dictionary might be something like
D1: CustomerName
D2: OrderNumber
D3: PartNumber
#ID 1234
0001:John Doe
0002:72832#VM83782#VM84783
0003:232-A#SVM2394-R#SVM3321-B#VM232-F#VM2342
CustomerName is a Single valued field. This is associated with entire record.
OrderNumber is a Value delimited list of Orders associated with at customer. In the SQL world this would be a child table.
PartNumber is a SubValue delimited list of Parts that is associated with each order. In the SQL world this would be a Child table of the Order Child Table.
Framing the logic like this, it really doesn't make any sense to say that you want to assign the 5th item on the next order the customer buys to be part "12345678" because you haven't got an order to associate with a part yet.
I believe there are some dictionary directives that you might be able to use to bypass this, but generally just know that it is bad form to create a sub-valued field without establishing an associated value first. When you start ignoring this you have to start validating for empty strings at ever turn. Down this road lies madness.
Hope that helps.
To summarize, you can't add a specific Sub Value to an unknown value. You have to first determine which value you want the subvalue mark to be in and then specify the subvalue.

Answer 2

From your code snippet
DYNAMIC.ARRAY = ' '
DYNAMIC.ARRAY<1,-1,5> = '1,1,5' ;* Adds to 1,1,1 not 1,1,5 when DYNAMIC.ARRAY contains only whitespaces before this operation
There are a number of things to be aware of
1) The white spaces have no bearing on what happens, as long as there are no reserved characters in the ASCII string (#FM,#AM,#VM,#SVM characters) the result will be the same.
2) The '-1' option should always be the last option and putting it in the second last parameter position will not work.
What you are trying to achive can be performed in many different ways
DYNAMIC.ARRAY<1,-1> = #SVM:#SVM:#SVM:#SVM:"1,1,5" ;* appends subvalued string as last value
or
DYNAMIC.ARRAY<1,-1> = STR(#SVM,4):"1,1,5" ;* appends subvalued string as last value
or
TEMP = "" ;* needs to be initialised
TEMP<1,1,5> = "1,1,5" ;* puts string in 5th subvalue position
DYNAMIC.ARRAY<1,-1> = TEMP ;* appends TEMP string as last value
or
VAL.POS = DCOUNT(DYNAMIC.ARRAY<1,1>,#VM) ;* find next value position
DYNAMIC.ARRAY<1,VAL.POS,5> = "1,1,5" ;* insert string into subvalue 5 of value

Answer 3

The '-1' use in inserting data into a dynamic array is a special notation, with its own rules. Using -1 essentially means "insert after last attribute, value or sub-value" (depending on where you have the -1 in your expression).
In your first example:
DYNAMIC.ARRAY = ' '
DYNAMIC.ARRAY<1,-1,5> = '1,1,5'
You are saying put the string '1,1,5' in the first attribute, AFTER THE LAST MULTIVALUE, as the 5th sub-value.
I would expect this to place the string '1,1,5' in position <1,2,5> because the -1 in the 'value' position says "put after last value" and because your initial array value was a single string of spaces, you already have something in array location <1,1,1> so the -1 causes a new value position to be added, and the 5 defines the subvalue position. So, result is a value placed into <1,2,5>
In your second example:
DYNAMIC.ARRAY = ' '
DYNAMIC.ARRAY<-1> = '1,1,1'
DYNAMIC.ARRAY<1,-1,5> = '1,2,5'
You start with the first line setting the array to a single attribute containing a string of spaces. The next line (with the <-1>) is saying "add a new attribute with the value '1,1,1'" which means you now have an array with 2 attributes. The third line (with the <1,-1,5>) means insert the string '1,2,5' in the first attribute, AFTER THE LAST VALUE, as the 5th sub-value, so I would again expect the result to be the string '1,2,5' to be in <1,2,5>
My comments are based on what I'd expect to see using R83 Pick, you do not say what version or 'account flavour' of UniVerse you are using, so perhaps that is part of the issue here.
It may be that the initial array of whitespace is being seen as an 'empty/null attribute' by UniVerse. I assume if you change the whitespace value in your first example to say 'ABC' then it all works as expected?