Empty or null values in units or label array

[rweigel]

In HAPI 2.1, an array of units or labels is allowed. What should be used when there is no unit or label for an element? Should "" and null be allowed?

I would think that if an array of labels is given, the elements must all be non-empty strings (because why would you want to not label one component?). If an array of units is given, then "" and null are both allowed and mean the same thing. Note that in the spec, we don't state what "" means for a unit that is a string.

size = [3]
labels = ["Bx","By",""] // No
labels = ["Bx","By","By/Bx"] // Yes
units = ["nT","nT",null] // OK
units = ["nT","nT","dimensionless"]  // OK
units = ["nT","nT",""] // If OK, then need to state units = "" is OK for
// case where units is a string and not an array

[jvandegriff]

I agree:

1. in the label array, all elements must be non-null and non-empty strings
2. in the units array, a null and an empty string are both interpreted as "dimensionless"

[jvandegriff]

update for 2.1.1 to clarify how the broadcasting works - examples to be added...

[jvandegriff]

For a non-array units value, we only allow a non-empty string, null or "dimensionless", so we should say the same for individual units elements in a units array. Above I said that within a units array, null and empty string would be interpreted as dimensionless. If we want that, we should update the description of a scalar units value to also allow the empty string.

[rweigel]

Give this, only null and "dimensionless" should be allowed.