Thanks, James! What still throws me off is that the JoC book points out a symmetry that I wanted to better grasp. It first notes that:
* `(first []) ;=> nil` and * `(rest []) ;=> ()` and then goes on to say: * "Clojure functions that promise to return sequences, such as `map` and `filter`, work the same way as `rest`." And, * (when calling `seq` on a coll) "...In either case, if the collection is empty, `seq` returns nil and never an empty sequence. Functions that promise to return seqs (not sequences), such as `next`, work the same way." Hm. "seqs (not sequences)" doesn't make sense to me here. Maybe I'm misunderstanding, or maybe there's a typo (or mis-capitalization) in there somewhere? -- John On Wednesday, October 8, 2014 8:16:38 PM UTC-4, James Reeves wrote: > > The words "seq" and "sequence" can be used interchangeably. > > The "map" and "filter" functions return seqs. > > Yes, a seq may be lazy, but vectors and lists cannot. > > "seqable" means any data structure that can be turned into a seq using the > "seq" function. This includes the Clojure collections, but also strings, > arrays and Java collections. > > The Sequential interface is a way of indicating a collection has a natural > order. So seqs, lists and vectors are sequential, but maps and sets are not. > > The ISeq interface is the internal interface for seqs. An object is a seq > if it implements ISeq. > > - James > > > On 8 October 2014 19:39, John Gabriele <jmg...@gmail.com <javascript:>> > wrote: > >> Reading Joy of Clojure, section 5.1.2, I'm hoping someone here can help >> me understand the following: >> >> * `clojure.core/seq` returns a "seq" or a "sequence"? Likewise for >> `map` and `filter`. >> >> * What is the difference between a "seq" and a "sequence"? >> >> * A seq may possibly be lazy, but vectors and lists are always >> fully-realized, correct? >> >> * What does "seqable" mean? >> >> * Is Seq (ISeq?) or is Sequential the `first`/`rest` API? What is the >> difference between ISeq and Sequential (see `seq?` & `sequential?`)? >> >> Thanks! >> >> -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
