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Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
60 lines
1.6 KiB
Plaintext
60 lines
1.6 KiB
Plaintext
; feed/thread — conversation threading. A reply carries :reply-to <parent-object>
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; (normalize preserves it). A thread is the transitive closure over :reply-to from
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; a root object: root + replies + replies-to-replies, gathered chronologically.
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;
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; Requires: lib/feed/normalize.sx, lib/feed/stream.sx, lib/feed/fanout.sx
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; (feed/-elem?, feed/-distinct).
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; direct replies to an object
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(define
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feed/replies
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(fn
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(stream object)
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(feed/filter stream (fn (a) (equal? (get a :reply-to) object)))))
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(define
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feed/reply-count
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(fn (stream object) (feed/count (feed/replies stream object))))
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; iterate f from x until the result stops growing (set-closure fixpoint)
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(define
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feed/-fixpoint
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(fn
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(f x)
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(let
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((nx (f x)))
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(if (= (len nx) (len x)) x (feed/-fixpoint f nx)))))
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; the set of object-ids in the thread rooted at `root`
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(define
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feed/thread-objects
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(fn
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(stream root)
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(let
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((all (feed/items stream)))
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(feed/-fixpoint
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(fn
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(acc)
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(feed/-distinct
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(append
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acc
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(map
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(fn (a) (get a :object))
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(filter (fn (a) (feed/-elem? (get a :reply-to) acc)) all)))))
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(list root)))))
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; the full thread as a chronological stream (root + all descendants)
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(define
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feed/thread
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(fn
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(stream root)
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(let
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((objs (feed/thread-objects stream root)))
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(feed/sort-by-at
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(feed/filter stream (fn (a) (feed/-elem? (get a :object) objs)))))))
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; how many activities are in the thread (root counts as 1)
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(define
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feed/thread-size
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(fn (stream root) (feed/count (feed/thread stream root))))
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