Predicate types?

[davenewza]

Is there any way to define a type which is a predicate?

For example, we have defined the function sum(...) which might be used like this: sum(invoice.items.total). In this case, invoice would be defined as a variable of some struct type in the expression context. However, we'd like to add a second parameter, a predicate, which would be used to indicate a filter expression. For example, sum(invoice.items.total, x => !x.isDeleted). I understand that this syntax isn't valid CEL, but could there be another way to represent a predicate somehow?

[davenewza]

@TristonianJones Sorry to ping you directly, but perhaps you might have a quick answer?

[TristonianJones]

Hi @davenewza, you'll want to use the Fold API within cel-go to create a new macro that does what you're considering. This is similar to the sortBy macro implementation done here: #1037