Comparative for user defined type?

Authoring Inform 7
#1

I have the following code:

Size is a kind of value. The sizes are tiny, little, midsized, big and huge. A thing has a size. Definition: A thing is large if its size is big or more.
It gives the following error:

Problem. You gave as a definition 'A thing is large if its size is big or more'  : but that definition is wrongly phrased, assuming it was meant to be a grading adjective like 'Definition: a container is large if its carrying capacity is 10 or more.'

Am I doing something wrong, or is it just impossible to define comparatives based on enumerated values?
Enumerated values can be compared (“the size of A is greater than the size of B”), so it seems like it should be possible to define the comparative (and have “A is larger than B”).

Many thanks!

#2

Seems like it’s impossible, although as you say, there’s no obvious reason why it should be.

#3

Looks like this wording works:

Definition: A thing is large if the size of it is at least big.
#4

That defines “large”, but not “larger” / “largest”.

#5

Thanks!

I ended up simulating “to be larger/smaller than” as verbs implying (or reverse implying) the same conditional relation, and "the largest/smallest " as two separate (and rather wordy) phrases that work through the full logic.

Not very elegant, but will hold the fort until a better solution is created/discovered.