Can someone steeped in type theory explain the following:
I never understood why the default for [a] means that the list could be empty. If ...
foo: [a] -> a
... foo is supposed to get a list of a's, it should get a list of a's, with at least one a. If the list can be empty, then explicitly annotate it so:
foo: [a*] -> a
One way or the other one has to deal with the empty list explicitly (in the signature). If you allow empty lists, it will have to return a 'Maybe a'. It seems to me that it just makes processing the result easier in the common case if the input were to be constrained.
I never understood why the default for [a] means that the list could be empty. If ...
... foo is supposed to get a list of a's, it should get a list of a's, with at least one a. If the list can be empty, then explicitly annotate it so: One way or the other one has to deal with the empty list explicitly (in the signature). If you allow empty lists, it will have to return a 'Maybe a'. It seems to me that it just makes processing the result easier in the common case if the input were to be constrained.