jolt's seq layer realized one element ahead of Clojure, so a side-effecting
lazy seq ran its producer too eagerly. Four changes bring it in line:
- rest is Clojure's more(): it returns the tail without realizing it. An
unforced tail (vector / string / lazy-seq cell) comes back as a deferred
seq, so (rest (iterate f x)) does not call f. next still realizes one.
- iterate applies f lazily, inside the tail thunk, so (first (iterate f x))
is x with no call to f (clojure.lang.Iterate parity).
- take realizes exactly n: the last element terminates without touching the
rest, instead of forcing one more element of the source.
- an empty realized lazy seq is still a sequence value, printing "()" not
"nil" (a JVM LazySeq is never nil).
Also: the map transducer's step fn now takes multiple inputs
([result input & inputs]) so a multi-collection transduce applies f across
all of them. Fixes medley's join/window/sequence-padded laziness and
multi-input transducer tests (now 293/293). The rest change also fixed a
latent overrun in distinct/dedupe over a map's empty tail.
iterate is a seed source, re-minted.
448611a5df