Clojurians Log v2
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clojure 2026-01-17
Coby Tamayo 2026-01-17T05:23:48.862469Z
I have this code for detecting whether something is a Datomic-style https://docs.datomic.com/query/query-data-reference.html#pull-expressions:
(defn- pull-expr? [expr]
(and (list? expr) (= 'pull (first expr))))expr e.g. turning it into a LazySeq before it gets to this fn. I fixed this by calling sequential? instead of list? but I'm wondering if this is a sound approach
seq? Is usually what you want instead of list?
Coby Tamayo 2026-01-17T07:22:15.913279Z
oh that makes sense, thanks
Coby Tamayo 2026-01-17T07:29:41.394309Z
side note, what is Sequential even for? the interface has no methods?
p-himik 2026-01-17T08:12:01.205429Z
A marker interface. To make sequential? work.
Coby Tamayo 2026-01-17T08:19:42.717229Z
it was funny having just read that and reading the docstring of sequential? again: Returns true if coll implements Sequential. An ouroboros of meaning, unfolding in an endless sequence...
Coby Tamayo 2026-01-17T08:20:10.558189Z
but I think I get it. sequential? is just whether or not a collection is ordered...?
p-himik 2026-01-17T08:25:42.858489Z
Yes, indeed. And of course it only works properly with Clojure types, so you cannot check arbitrary collection types with it. Although, I still don't know why e.g. a sorted map is not considered sequential.
1
Ben Sless 2026-01-17T11:20:59.236609Z
If you really want to be sure it's a valid pull expr https://github.com/bsless/datalog-parser.spec/blob/master/src/bsless/datalog_parser/spec.clj#L77