Transducer for partition-all with step
The docs for partition-all mention that when a coll is not provided, it returns a transducer. This is true for the form (partition-all n), but not true for (partition-all n step). There's no clear way that I can see to combine transducers from core to produce this sort of "sliding window" transducer, i.e.
user=> (into  (partition-all 2 1) [1 2 3 4 5])
((1 2) (2 3) (3 4) (4 5) (5))
Of course, there's an arity collision between the above hypothesized (partition-all n step) and the concrete, non-transducer-producing (partition-all n coll), which could be resolved by switching on the type of the second argument, or less hackily by providing the functionality in a separate function, e.g. (sliding window-size step-size), or perhaps by some other means.
I implemented this function with reference to the existing (partition-all n) transducer here: https://gist.github.com/nornagon/03b85fbc22b3613087f6
Would it make sense to work on getting something like this into core?