type.ordering_operand

A comparison such as < or > is used on a value that has no order, such as text or a value that may be none.

Area 3, Logic; not declinable; the next step is usually the agent's.

Why Jadpo refuses it

<, <=, > and >= put two values in order, so they work only where an order means something: numbers and time values of one named type. A value that may be none has no place in an order, and Jadpo won't guess whether none comes first or last. Text has no order either, because the order depends on the reader's language.

What it looks like

main.jadpo:

type Count = Int {}type Flag = Bool {}function over_maximum(count: Count?, maximum: Count) -> Flag {    return Flag(count > maximum)}

  |6 |     return Flag(count > maximum)  |                 ^^^^^ may be `none`

(agent) at the end of the next: line means your coding agent can make the fix itself.

Comparing two pieces of text with < is the same error:

main.jadpo:

type Name = Text {}type Flag = Bool {}function earlier(name: Name, other: Name) -> Flag {    return Flag(name < other)}

  |6 |     return Flag(name < other)  |                 ^^^^ this is `Name`

How to fix it

If the value may be none, match on it, compare inside some(...), and say what the answer is when there is no value:

    return match count {        some(known) -> Flag(known > maximum)        none -> false    }

A count that is there is compared with the maximum, and a missing count is never over it.

If you are putting text in order, sort a list of it with list.sort_by, giving the text as the key. main.jadpo becomes:

type Name = Text {}function in_order(names: List<Name>) -> List<Name> {    return list.sort_by(names, name -> name)}

The names come back sorted by their code points, the same order a query sorts text in. Given locale:, list.sort_by orders text by a language's rules instead (Lists). To check that two pieces of text are the same, compare them with ==.

Related

• Expressions and operators
• Values that may be missing
• Lists