Getting back unsafe head's type, safely
This library defines a type for strictly infinite (but lazy) lists.
As such, some of the
Data.List API is not implemented here -- anything that
relies on finiteness, for example -- while other functions get simplified types.
Also note that equality of countable sets is undecidable in general, but inequality
can be determined after a finite number of steps. As such using
may not terminate.
head :: forall a. List a -> a tail :: forall a. List a -> List a
are now totally safe.
Data.List.Infinite is meant to be imported qualified, as almost all its exposed
functions clash with other modules.
Note also that the
Semigroup instance provided is not extended by the finite
bower i --save purescript-infinite-lists
It's amusing that, had they been provided,
length could be given in O(1) time
instead of O(n), and
last could be given a simple definition, retaining the
same type signature:
last _ = Nothing.