Seq function returns

[puredanger]

In general, it is most flexible for sequence functions to be spec'ed as taking seqable? and returning seqable? (not seq?). The reasons for this are quite subtle, but there is a performance advantage to be had in cases where a sequence function can return something that avoids forcing the seq. We ran into this when the reducing/seqable work was done on range/cycle/iterate/repeat in 1.7. So, I'd just urge seqable? as the most generic alternative in most of those.

[borkdude]

@puredanger Out of curiosity and documentation purposes I’d like to know some examples of this:

where a sequence function can return something that avoids forcing the seq

How can this be used if you cannot rely on a sequence function returning a sequence? You'd still have to call seq on it to be able to use it as a sequence?

[puredanger]

All sequence functions call seq on their inputs so "using" it already does this.