Streams supporting unbounded search. Technically, all streams should be infinite, but for efficiency, we allow them to be truncated. As such, it is impossible to define a general null predicate for streams. Here, we have null return true for the particular case that the stream is an empty list.
include BaseLazyPlus with type 'a m = 'a t Lazy.tinclude BatInterfaces.Monad with type 'a m = 'a t Lazy.tMonadic binding.
bind m f executes first m then f, using the result of m.
val return : 'a -> 'a mReturn a value, that is, put a value in the monad.
val zero : unit -> 'a mval null : 'a m -> boolnull x implies that x is zero. If you do not want to or cannot answer whether a given x is zero, then null x should be false.