discerne type patterns

Discerne cases can test nominal type members and bind the narrowed value.

Syntax: मिलाओ <union> { स्थिति <type> स्थिर <name> { ... } }

Category#

control-flow

Related#

• मिलाओ
• स्थिति
• विभेद
• है

Examples#

radix/corpus/discerne/type-patterns.fab (canonical · feature)#

Discerne cases can test nominal type members and bind the narrowed value.

# Type-pattern cases use the same member predicate as `है` and bind the
# narrowed value for the arm body.
class Formal {
    var string greeting
}

class Casual {
    var string greeting
}

fn classify(Formal ∪ Casual u) → string {
    match u {
        case Formal const f {
            return f.greeting
        }
        case Casual const c {
            return c.greeting
        }
    }
}

main {
    const Formal f ← Formal { greeting = "formal" }
    const Casual c ← Casual { greeting = "casual" }
    print classify(f)
    print classify(c)
}

Expected output:

formal
casual