chapter eight
This chapter groups together the functions that can be used consistently across different data structures. Their consistency is expressed by one of the following properties or combination thereof:
- Their performance is consistent across different collections with little or no appreciable difference.
- Even if there are performance differences, their use is idiomatic across different data structures.
- The function gets the work done so quickly that the trade-off of using it against the "wrong" data structure is acceptable.
- The function has been designed to be polymorphic and to operate on different collections.
The chapter is further divided into additional sub-chapters. We are going to first have a look at the basics functions to create, count or otherwise access a collection in the most general way. Next are the functions designed to be polymorphic. Finally, the last sub-chapter is dedicated to general purpose functions like grouping, sorting, partitioning and others that are very common in every day use.
Listing 8.1. → Collection copy, Transducers
(into ([]) ([to]) ([to from]) ([to xform from]))
into is a frequently used function in the Clojure standard library. into copies the content of a collection into another:
(into #{} (range 10))
;; #{0 7 1 4 6 3 2 9 5 8} ; #1
(into [:g :x :d] [1 5 9])
;; [:g :x :d 1 9 5] ; #2