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

• ← Runtime Polymorphism
• Sequence Comprehensions →

10. Lazy Sequences - Koans Walkthrough

This video covers lazy sequences. Clojure has extensive support for lazy sequences, which defer the calculation of values for as long as possible.

Here is the 10_lazy_sequences.clj source code:

(meditations
  "There are a wide range of ways to generate a sequence"
  (= __ (range 1 5))

  "The range starts at the beginning by default"
  (= __ (range 5))

  "It's important to only take what you need from a big sequence"
  (= [0 1 2 3 4 5 6 7 8 9]
     (take __ (range 100)))

  "You can also limit results by dropping what you don't need"
  (= [95 96 97 98 99]
     (drop __ (range 100)))

  "Iteration provides an infinite lazy sequence"
  (= __ (take 20 (iterate inc 0)))

  "Repetition is key"
  (= [:a :a :a :a :a :a :a :a :a :a ]
     (repeat 10 __))

  "Iteration can be used for repetition"
  (= (repeat 100 :foo)
     (take 100 (iterate ___ :foo))))