Clojure Koans Walkthrough

1. Introduction
2. Lists
3. Vectors
4. Sets
5. Maps
6. Functions
7. Conditionals
8. Higher Order Functions
9. Runtime Polymorphism
10. Lazy Sequences
11. Sequence Comprehensions
12. Creating Functions
13. Recursion
14. Destructuring
15. Refs
16. Atoms
17. Macros
18. Datatypes
19. Java Interop
20. Partition

Recommended Books

• ← Java Interop

20. Partition - Koans Walkthrough

This video introduces the partition function, which is a powerful function for partitioning a lazy sequence into groups of lists, of any size. You can also specify a step value (or offset) that lets you easily get sliding-window functionality for free.

Here is the 20_partition.clj source code:

(meditations
  "To split a collection you can use the partition function"
  (= '((0 1) (2 3)) (__ 2 (range 4)))

  "But watch out if there are not enough elements to form n sequences"
  (= '(__) (partition 3 [:a :b :c :d :e]))

  "You can use partition-all to also get partitions with less then n elements"
  (= __ (partition-all 3 (range 5)))

  "If you need to, you can start each sequence with an offset"
  (= '((0 1 2) (5 6 7) (10 11 12)) (partition 3 __ (range 13)))

  "Consider padding the last sequence with some default values.."
  (= '((0 1 2) (3 4 5) (6 :hello)) (partition 3 3 [__] (range 7)))

  ".. but notice that they will only pad up to given sequence length"
  (= '((0 1 2) (3 4 5) __) (partition 3 3 [:this :are "my" "words"] (range 7))))