4 ms·
Checking whether mf.type is NOTHING or JUST is your boolean. It's linked by providence to whether or not getFoo() is a runtime exception. With a true ADT getFoo
by tel 12y ago
Checking whether mf.type is NOTHING or JUST is your boolean. It's linked by providence to whether or not getFoo() is a runtime exception. With a true ADT getFoo would not be accessible unless mf.type == JUST, but in this example it's up to the programmer to enforce that providence.
So that's the blindness. The pre/post conditions around how mf.type relates to its surroundings cannot be expressed first-class in the code. You are required to do risky things like call potentially partial code.
- dllthomas 12y agoSo it's specifically the separation of the check and the action? I totally agree this is undesirable; I understood "boolean blindness" to be closer to "bare primitive types lack meaning", specialized to Bool.
- tel 12y agoI always think of it as your data types being too unrestricted so as to allow for invalid states. The eliminator for Maybe (a -> r) -> r -> Maybe a -> r means you only access the `a` if it's there and the access/matching are inextricably linked. So, I think "bare primitive types lack meaning" is basically correct given that you interpret "meaning" as "meaningful uses/actions".
- dllthomas 12y agoYeah, given the nature of the types involved here, I think the two concepts I was trying to distinguish are not as far apart as I'd thought.