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203
.gitignore vendored
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@ -1,206 +1,11 @@
*~
bin bin
classes
lib
releases releases
target
*.jar *.jar
# Created by https://www.gitignore.io/api/clojure,osx,linux,windows,leiningen,intellij,eclipse,sublimetext
### Clojure ###
pom.xml
pom.xml.asc
*jar
/lib/
/classes/
/target/
/checkouts/
.lein-deps-sum
.lein-repl-history
.lein-plugins/
.lein-failures
.nrepl-port
### OSX ###
.DS_Store .DS_Store
.AppleDouble
.LSOverride
# Icon must end with two \r
Icon
# Thumbnails
._*
# Files that might appear in the root of a volume
.DocumentRevisions-V100
.fseventsd
.Spotlight-V100
.TemporaryItems
.Trashes
.VolumeIcon.icns
# Directories potentially created on remote AFP share
.AppleDB
.AppleDesktop
Network Trash Folder
Temporary Items
.apdisk
### Linux ###
*~
# KDE directory preferences
.directory
# Linux trash folder which might appear on any partition or disk
.Trash-*
### Windows ###
# Windows image file caches
Thumbs.db
ehthumbs.db
# Folder config file
Desktop.ini
# Recycle Bin used on file shares
$RECYCLE.BIN/
# Windows Installer files
*.cab
*.msi
*.msm
*.msp
# Windows shortcuts
*.lnk
### Leiningen ###
pom.xml
pom.xml.asc
*jar
/lib/
/classes/
/target/
/checkouts/
.lein-deps-sum .lein-deps-sum
.lein-plugins
.lein-repl-history .lein-repl-history
.lein-plugins/
.lein-failures
.nrepl-port
### Intellij ###
# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio
*.iml
## Directory-based project format:
.idea/
# if you remove the above rule, at least ignore the following:
# User-specific stuff:
# .idea/workspace.xml
# .idea/tasks.xml
# .idea/dictionaries
# Sensitive or high-churn files:
# .idea/dataSources.ids
# .idea/dataSources.xml
# .idea/sqlDataSources.xml
# .idea/dynamic.xml
# .idea/uiDesigner.xml
# Gradle:
# .idea/gradle.xml
# .idea/libraries
# Mongo Explorer plugin:
# .idea/mongoSettings.xml
## File-based project format:
*.ipr
*.iws
## Plugin-specific files:
# IntelliJ
/out/
# mpeltonen/sbt-idea plugin
.idea_modules/
# JIRA plugin
atlassian-ide-plugin.xml
# Crashlytics plugin (for Android Studio and IntelliJ)
com_crashlytics_export_strings.xml
crashlytics.properties
crashlytics-build.properties
### Eclipse ###
*.pydevproject
.metadata
.gradle
bin/
tmp/
*.tmp
*.bak
*.swp
*~.nib
local.properties
.settings/
.loadpath
# Eclipse Core
.project
# External tool builders
.externalToolBuilders/
# Locally stored "Eclipse launch configurations"
*.launch
# CDT-specific
.cproject
# JDT-specific (Eclipse Java Development Tools)
.classpath
# Java annotation processor (APT)
.factorypath
# PDT-specific
.buildpath
# sbteclipse plugin
.target
# TeXlipse plugin
.texlipse
### SublimeText ###
# cache files for sublime text
*.tmlanguage.cache
*.tmPreferences.cache
*.stTheme.cache
# workspace files are user-specific
*.sublime-workspace
# project files should be checked into the repository, unless a significant
# proportion of contributors will probably not be using SublimeText
# *.sublime-project
# sftp configuration file
sftp-config.json
# Vagrant
.vagrant/
ubuntu-xenial-16.04-cloudimg-console.log

133
README.md
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@ -1,88 +1,61 @@
# Clojure Koans # Clojure Koans
The Clojure Koans are a fun way to get started with Clojure - no experience The Clojure Koans are a fun and easy way to get started with Clojure - no
assumed or required. Follow the instructions below to start making tests pass! experience assumed or required. Just follow the instructions below to start
making tests pass!
## Getting Started ### Getting Started
I recommend starting from a cloned or forked repo. This way you'll be able to The easiest and fastest way to get the koans up and running is to [download the
track your progress in Git. You might want to create your own branch - that way latest zip file from Github](https://github.com/functional-koans/clojure-koans/downloads).
if you pull back the latest koans from master, it'll be a bit easier to manage This way, you'll have all the dependencies you need, including Clojure itself
the inevitable conflicts if we make changes to exercises you've already and JLine, and you can skip the rest of this section (skip to "Running the
completed. Koans").
You have a few options for installation: If you're starting from a cloned or forked repo, that's cool too. This way
you'll be able to track your progress in Git, and see how your answers compare
- Install the dependencies for the koans (such as Clojure) on your machine to others, by checking out the project's Network tab. You might want to create
- Use Vagrant and the configuration in this repository your own branch - that way if you pull back the latest koans from master, it'll
- Use Docker be a bit easier to manage the inevitable conflicts if we make changes to
exercises you've already completed.
Instructions for each option are below!
### Installation on Your Machine
The only things you'll need to run the Clojure Koans are: The only things you'll need to run the Clojure Koans are:
- JDK (I suggest version 8, but anything 6 or above should work fine) - JRE 1.5 or higher
- [Leiningen](http://github.com/technomancy/leiningen), a build tool for Clojure - [clojure-1.5.1.jar](http://repo1.maven.org/maven2/org/clojure/clojure/1.5.1/clojure-1.5.1.zip)
Once you've cloned this repo and installed the dependencies, you can run: You can use [Leiningen](http://github.com/technomancy/leiningen) to
automatically install the Clojure jar in the right place. Leiningen will also
get you a couple more jarfiles, including JLine, which allows you some of the
functionality of readline (command-line history, for example).
``` ### Installing dependencies
lein repl
```
to make sure all the dependencies get downloaded properly (and then `(exit)` Dependencies are installed automatically with lein 2, but if for some reason
when you want to quit). See below for details on the REPL. you're on lein 1 and can't upgrade, you'll need to run
`lein deps`
### Installation with Vagrant which will download all dependencies you need to run the Clojure koans.
Make sure you have [Vagrant](https://www.vagrantup.com/) and I strongly recommend that you upgrade to lein 2 instead!
[VirtualBox](https://www.virtualbox.org) installed.
In the root directory of the project, execute:
``` ### Running the Koans
vagrant up
vagrant ssh
cd /vagrant
lein koan run
```
If you're running from the zipfile, simply run
### Installation with Docker `script/run` on Mac/\*nix
Once you've got [Docker](https://www.docker.com/) installed, you're basically `script\run` on Windows
all set. You can run these commands to get started:
To run koans: If you're running from a checkout using lein 2, run the koans via
```
docker run --rm -it -v $(pwd):/app -w /app clojure lein koan run
```
To start up a REPL:
```
docker run --rm -it -v $(pwd):/app -w /app clojure lein repl
```
## Running the Koans
Run the koans via:
`lein koan run` `lein koan run`
If want to run directly from a REPL, once you are inside the `lein repl` prompt you can run the koans with It's an auto-runner, so as you save your files with the correct answers, it will
advance you to the next koan or file (conveniently, all files are prefixed with
`(exec "run")` the sequence that you should follow).
Either way, it's an auto-runner, so as you save your files with the correct
answers, it will advance you to the next koan or file (conveniently, all files
are prefixed with the sequence that you should follow).
You'll see something like this: You'll see something like this:
@ -93,7 +66,7 @@ You'll see something like this:
(= __ true) (= __ true)
The output is telling you that you have a failing test in the file named The output is telling you that you have a failing test in the file named
`01_equalities.clj`, on line 3. So you need to open that file up and make `01_equalities.clj`, on line 3. So you just need to open that file up and make
it pass! You'll always be filling in the blanks to make tests pass. it pass! You'll always be filling in the blanks to make tests pass.
Sometimes there could be several correct answers (or even an infinite number): Sometimes there could be several correct answers (or even an infinite number):
any of them will work in these cases. Some tests will pass even if you replace any of them will work in these cases. Some tests will pass even if you replace
@ -102,24 +75,24 @@ you give one correct expression to replace each blank.
The koans differ from normal TDD in that the tests are already written for you, The koans differ from normal TDD in that the tests are already written for you,
so you'll have to pay close attention to the failure messages, because up until so you'll have to pay close attention to the failure messages, because up until
the very end, making a test pass means that the next failure message comes the very end, making a test pass just means that the next failure message comes
up. up.
While it might be easy (especially at first) to fill in the blanks making While it might be easy (especially at first) to just fill in the blanks making
things pass, you should work thoughtfully, making sure you understand why the things pass, you should work thoughtfully, making sure you understand why the
answer is what it is. Enjoy your path to Clojure enlightenment! answer is what it is. Enjoy your path to Clojure enlightenment!
## Trying more things out ### Trying more things out
It's very useful to try things out in a REPL (Read-Evaluate-Print Loop) There's a REPL (Read-Evaluate-Print Loop) included in the Clojure Koans. Just
whenever you get stuck or curious. Run: run:
``` `script/repl` on Mac/\*nix
lein repl
```
and you'll be able to type expressions in, and see what output they produce. `script\repl` on Windows
If you're on lein 2, `lein repl` is what you want instead.
Here are some interesting commands you might try, once you're in a running REPL: Here are some interesting commands you might try, once you're in a running REPL:
@ -138,10 +111,10 @@ And if those still don't make sense:
will show you what those commands mean. will show you what those commands mean.
You can exit the REPL with `CTRL-d`, `(exit)`, or `(quit)`. You can exit the REPL with `CTRL-d` on any OS.
## Contributing ### Contributing
Patches are encouraged! Make sure the answer sheet still passes Patches are encouraged! Make sure the answer sheet still passes
(`lein koan test`), and send a pull request. (`lein koan test`), and send a pull request.
@ -152,32 +125,32 @@ to add to existing koans. So write some fun exercises, add your answers to
Please follow the guidelines in Please follow the guidelines in
http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html for http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html for
commit messages, and put your code in a feature branch (not master) before commmit messages, and put your code in a feature branch (not master) before
making the pull request. This makes patches easier to review. making the pull request. This makes patches easier to review.
Feel free to contact me (Colin Jones / trptcolin) on Github or elsewhere if you Feel free to contact me (Colin Jones / trptcolin) on Github or elsewhere if you
have any questions or want more direction before you start pitching in. have any questions or want more direction before you start pitching in.
## Contributors ### Contributors
https://github.com/functional-koans/clojure-koans/contributors https://github.com/functional-koans/clojure-koans/contributors
## Credits ### Credits
These exercises were started by [Aaron Bedra](http://github.com/abedra) of These exercises were started by [Aaron Bedra](http://github.com/abedra) of
[Relevance, Inc.](http://github.com/relevance) in early 2010, as a learning [Relevance, Inc.](http://github.com/relevance) in early 2010, as a learning
tool for newcomers to functional programming. Aaron's macro-fu makes these tool for newcomers to functional programming. Aaron's macro-fu makes these
koans clear and fun to use and improve upon, and without Relevance's koans extremely simple and fun to use, and to improve upon, and without
initiative, this project would not exist. Relevance's initiative, this project would not exist.
Using the [koans](http://en.wikipedia.org/wiki/koan) metaphor as a tool for Using the [koans](http://en.wikipedia.org/wiki/koan) metaphor as a tool for
learning a programming language started with the learning a programming language started with the
[Ruby Koans](http://rubykoans.com) by [EdgeCase](http://github.com/edgecase). [Ruby Koans](http://rubykoans.com) by [EdgeCase](http://github.com/edgecase).
## License ### License
The use and distribution terms for this software are covered by the The use and distribution terms for this software are covered by the
Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)

31
Vagrantfile vendored
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@ -1,31 +0,0 @@
Vagrant.configure("2") do |config|
config.vm.box = "ubuntu/xenial64"
config.vm.network "private_network", ip: "192.168.33.33"
config.vm.provider "virtualbox" do |vb|
vb.memory = "1024"
end
config.vm.provision "shell", inline: <<-SHELL
set -x
#apt-get update
#apt-get upgrade -y
apt-get install -y openjdk-8-jdk
SHELL
config.vm.provision "shell", privileged: false, inline: <<-SHELL
pwd
mkdir bin
echo "PATH=\$PATH:~/bin" >> .bashrc
cd bin
wget https://raw.githubusercontent.com/technomancy/leiningen/stable/bin/lein
chmod +x lein
./lein
cd /vagrant
~/bin/lein deps
SHELL
end

7
ideaboard.txt
View file

@ -1,16 +1,16 @@
Concepts / Language Features Concepts / Language Features
===== =====
Quoting
new record syntax new record syntax
Agents Agents
Vars Vars
state identity lifetime state identity lifetime
Metadata
immutability / side effects immutability / side effects
type hints type hints
Pre and Post conditions of functions Pre and Post conditions of functions
ex-info/ex-data
reducers (?)
transducers (?) - maybe just some basic ones, nothing too crazy
Particular Functions Particular Functions
===== =====
@ -27,3 +27,4 @@ map-indexed
partition-all partition-all
partition-by partition-by
repeatedly repeatedly

14
project.clj
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@ -1,10 +1,10 @@
(defproject clojure-koans "0.5.2-SNAPSHOT" (defproject clojure-koans "0.5.0"
:description "The Clojure koans." :description "The Clojure koans."
:dependencies [[org.clojure/clojure "1.10.0"] :dependencies [[org.clojure/clojure "1.5.1"]
[koan-engine "0.2.5"]] [koan-engine "0.2.3"]]
:dev-dependencies [[lein-koan "0.1.5"]] :dev-dependencies [[lein-koan "0.1.3"]]
:profiles {:dev {:dependencies [[lein-koan "0.1.5"]]}} :profiles {:dev {:dependencies [[lein-koan "0.1.3"]]}}
:repl-options {:init-ns koan-engine.runner :repl-options {:init-ns koan-engine.runner
:init ^:displace (do (use '[koan-engine.core]))} :init (do (use '[koan-engine.core]))}
:plugins [[lein-koan "0.1.5"]] :plugins [[lein-koan "0.1.3"]]
:main koan-engine.runner/exec) :main koan-engine.runner/exec)

154
resources/koans.clj
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@ -6,36 +6,11 @@
true true
true true
false false
"hello" "foo"
"hello" "foo"
nil
3]}] 3]}]
["02_strings" {"__" ["hello" ["02_lists" {"__" [1 2 3 4 5
"world"
"Cool "
"right?"
0
11
false
6 11
"123"
", "
"1" "2" "3"
"olleh"
"hello"
13
nil
"hello world"
true
false
false
"a"
true
true
false]}]
["03_lists" {"__" [1 2 3 4 5
1 1
[2 3 4 5] [2 3 4 5]
3 3
@ -48,7 +23,7 @@
"No dice!" "No dice!"
()]}] ()]}]
["04_vectors" {"__" [1 ["03_vectors" {"__" [1
[1] [1]
[nil nil] [nil nil]
2 2
@ -59,53 +34,50 @@
[:butter :and] [:butter :and]
3]}] 3]}]
["05_sets" {"__" [[3] ["04_sets" {"__" [[3]
3 3
#{1 2 3 4 5} #{1 2 3 4 5}
#{1 2 3 4 5} #{1 2 3 4 5}
#{2 3} #{2 3}
#{1 4}]}] #{1 4}]}]
["06_maps" {"__" [:b 2 ["05_maps" {"__" [:b 2
1 1
2 2
2 2
1 1
1 1
"Sochi" "Vancouver"
nil nil
:key-not-found :key-not-found
true true
false false
"February" "February"
1 "January" 1 "January"
:c 3 2006 2010 2014
2 "Sochi" "Torino" "Vancouver"]}]
2010 2014 2018
"PyeongChang" "Sochi" "Vancouver"
2 3]}]
["07_functions" {"__" [81 ["06_functions" {"__" [81
20 20
10 10
60 60
15 15
"AACC"] 30]
"___" [+ "___" [+
* *
(fn [f] (f 5)) (fn [f] (f 5))
(fn [f] (f 5))]}] (fn [f] (f 5))]}]
["08_conditionals" {"__" [:a ["07_conditionals" {"__" [:a
[] []
nil nil
:glory :glory
4 6 :your-road 4 6 :your-road
1 1
:bicycling :cocked-pistol
"is that even exercise?"]}] :say-what?]}]
["09_higher_order_functions" {"__" [4 8 12 ["08_higher_order_functions" {"__" [4 8 12
(* x x) (* x x)
[false false true false false] [false false true false false]
() ()
@ -116,29 +88,29 @@
100 100
(count a) (count b)]}] (count a) (count b)]}]
["10_runtime_polymorphism" {"__" [(str (:name a) " eats veggies.") ["09_runtime_polymorphism" {"__" [(str (:name a) " eats veggies.")
(str (:name a) " eats animals.") (str (:name a) " eats animals.")
(str "I don't know what " (:name a) " eats.") (str "I don't know what " (:name a) " eats.")
"Hello World!" "Hello World!"
"Hello, you silly world." "Hello, you silly world."
"Hello to this group: Peter, Paul, Mary!" ]}] "Hello to this group: Peter, Paul, Mary!" ]}]
["11_lazy_sequences" {"__" [[1 2 3 4] ["10_lazy_sequences" {"__" [[1 2 3 4]
[0 1 2 3 4] [0 1 2 3 4]
10 10
95 95
[1 2 4 8 16 32 64 128] (range 20)
:a] :a]
"___" [(fn [x] x)]}] "___" [(fn [x] x)]}]
["12_sequence_comprehensions" {"__" [[0 1 2 3 4 5] ["11_sequence_comprehensions" {"__" [[0 1 2 3 4 5]
(* x x) (* x x)
(range 10) (range 10)
(odd? x) (* x x) (odd? x) (* x x)
[row column] [row column]
]}] ]}]
["13_creating_functions" {"__" [true false true ["12_creating_functions" {"__" [true false true
4 4
:a :b :c :d :a :b :c :d
:c :d :c :d
@ -148,7 +120,7 @@
multiply-by-5 multiply-by-5
(comp dec square)]}] (comp dec square)]}]
["14_recursion" {"__" [true ["13_recursion" {"__" [true
acc acc
(loop [coll coll (loop [coll coll
acc ()] acc ()]
@ -162,10 +134,10 @@
(recur (dec n) (* acc n))))] (recur (dec n) (* acc n))))]
"___" [not]}] "___" [not]}]
["15_destructuring" {"__" [":bar:foo" ["14_destructuring" {"__" [":bar:foo"
(format (str "An Oxford comma list of %s, " (format (str "First comes %s, "
"%s, " "then comes %s, "
"and %s.") "then comes %s with the baby carriage")
a b c) a b c)
(apply str (apply str
(interpose " " (interpose " "
@ -184,7 +156,7 @@
street-address ", " city ", " state)) street-address ", " city ", " state))
]}] ]}]
["16_refs" {"__" ["hello" ["15_refs" {"__" ["hello"
"hello" "hello"
"better" "better"
"better!!!" "better!!!"
@ -193,7 +165,7 @@
] ]
"___" [(fn [x] (+ 20 x))]}] "___" [(fn [x] (+ 20 x))]}]
["17_atoms" {"__" [0 ["16_atoms" {"__" [0
1 1
(swap! atomic-clock (partial + 4)) (swap! atomic-clock (partial + 4))
20 20
@ -201,15 +173,17 @@
atomic-clock 20 :fin atomic-clock 20 :fin
]}] ]}]
["18_quote" {"__" ['(1 2 3 4 5) ["17_macros" {"__" [~(first form)
(1 2 3 4 5) ~(nth form 2)
'age form
quote (drop 2 form)
'(+ 2 3) "Hello, Macros!"
1 2 3 10
1 5]}] '(+ 9 1)
'(* 10 2)
'(+ 10 (2 * 3))]}]
["19_datatypes" {"__" [(print ["18_datatypes" {"__" [(print
(str "You're really the " (str "You're really the "
(.category this) (.category this)
", " recipient "... sorry.")) ", " recipient "... sorry."))
@ -221,68 +195,28 @@
(str "Congratulations on your Best Picture Oscar, " (str "Congratulations on your Best Picture Oscar, "
"Evil Alien Conquerors!")]}] "Evil Alien Conquerors!")]}]
["20_java_interop" {"__" [java.lang.String ["19_java_interop" {"__" [java.lang.String
"SELECT * FROM" "SELECT * FROM"
10 10
1024 1024
] ]
"___" [#(.toUpperCase %) "___" [#(.toUpperCase %)
]}] ]
}]
["21_partition" {"__" [partition ["20_partition" {"__" [partition
[:a :b :c] [:a :b :c]
'((0 1 2) (3 4)) '((0 1 2) (3 4))
5 5
:hello :hello
(6 :these :are) (6 :these :are)
]}] ]}]
["21_group_by" {"__" [odd?
["22_group_by" {"__" [odd?
{5 ["hello" "world"] 3 ["foo" "bar"]} {5 ["hello" "world"] 3 ["foo" "bar"]}
{1 [{:name "Bob" :id 1} {1 [{:name "Bob" :id 1}
{:last-name "Smith" :id 1}] {:last-name "Smith" :id 1}]
2 [{:name "Jennifer" :id 2}]} 2 [{:name "Mike" :id 2}]}
nil nil
{:naughty-list [{:name "Jimmy" :bad true} {:naughty-list [{:name "Jimmy" :bad true}
{:name "Joe" :bad true}] {:name "Joe" :bad true}]
:nice-list [{:name "Jane" :bad false}]}]}] :nice-list [{:name "Jack" :bad false}]}]}]
["23_meta" {"__" [{:league "National League"}
{:division "West"}
"This doesn't implement the IObj interface"
{:foo :bar}
nil
\C
inc
:park "Oracle Park"
'Giants
"Giants"]}]
["24_macros" {"__" [~(first form)
~(nth form 2)
form
(drop 2 form)
"Hello, Macros!"
10
'(+ 9 1)]}]
["25_threading_macros" {"__" [{:a 1}
"Hello world, and moon, and stars"
"String with a trailing space"
6
1
[2 3 4]
12
[1 2 3]]}]
["26_transducers" {"__" ['(2 3 4)
[2 4]
[2 4]
[2 4]
6]}]
["27_multimethods" {"__" ["Hello, World!"
"Hello there"
1
6]}]
] ]

9
src/koans/01_equalities.clj
View file

@ -24,16 +24,13 @@
(= __ (not (= 1 nil))) (= __ (not (= 1 nil)))
"Strings, and keywords, and symbols: oh my!" "Strings, and keywords, and symbols: oh my!"
(= __ (= "hello" :hello 'hello)) (= __ (= "foo" :foo 'foo))
"Make a keyword with your keyboard" "Make a keyword with your keyboard"
(= :hello (keyword __)) (= :foo (keyword __))
"Symbolism is all around us" "Symbolism is all around us"
(= 'hello (symbol __)) (= 'foo (symbol __))
"What could be equivalent to nothing?"
(= __ nil)
"When things cannot be equal, they must be different" "When things cannot be equal, they must be different"
(not= :fill-in-the-blank __)) (not= :fill-in-the-blank __))

3
src/koans/03_lists.clj → src/koans/02_lists.clj
View file

@ -1,4 +1,4 @@
(ns koans.03-lists (ns koans.02-lists
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(meditations (meditations
@ -43,3 +43,4 @@
(rest '()) (rest '())
(catch IllegalStateException e (catch IllegalStateException e
"No dice!")))) "No dice!"))))

70
src/koans/02_strings.clj
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@ -1,70 +0,0 @@
(ns koans.02-strings
(:require [koan-engine.core :refer :all]
[clojure.string :as string]))
(meditations
"A string is nothing more than text surrounded by double quotes"
(= __ "hello")
"But double quotes are just magic on top of something deeper"
(= __ (str 'world))
"You can do more than create strings, you can put them together"
(= "Cool right?" (str __ __))
"You can even get certain characters"
(= \C (get "Characters" __))
"Or even count the characters"
(= __ (count "Hello World"))
"But strings and characters are not the same"
(= __ (= \c "c"))
"What if you only wanted to get part of a string?"
(= "World" (subs "Hello World" __ __))
"How about joining together elements in a list?"
(= __ (string/join '(1 2 3)))
"What if you wanted to separate them out?"
(= "1, 2, 3" (string/join __ '(1 2 3)))
"Maybe you want to separate out all your lines"
(= [__ __ __] (string/split-lines "1\n2\n3"))
"You may want to make sure your words are backwards"
(= __ (string/reverse "hello"))
"Maybe you want to find the index of the first occurrence of a substring"
(= 0 (string/index-of "hello world" __))
"Or maybe the last index of the same substring"
(= __ (string/last-index-of "hello world, hello" "hello"))
"But when something doesn't exist, nothing is found"
(= __ (string/index-of "hello world" "bob"))
"Sometimes you don't want whitespace cluttering the front and back"
(= __ (string/trim " \nhello world \t \n"))
"You can check if something is a char"
(= __ (char? \c))
"But it may not be"
(= __ (char? "a"))
"But chars aren't strings"
(= __ (string? \b))
"Strings are strings"
(= true (string? __))
"Some strings may be blank"
(= __ (string/blank? ""))
"Even if at first glance they aren't"
(= __ (string/blank? " \n \t "))
"However, most strings aren't blank"
(= __ (string/blank? "hello?\nare you out there?")))

2
src/koans/04_vectors.clj → src/koans/03_vectors.clj
View file

@ -1,4 +1,4 @@
(ns koans.04-vectors (ns koans.03-vectors
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(meditations (meditations

13
src/koans/05_sets.clj → src/koans/04_sets.clj
View file

@ -1,6 +1,5 @@
(ns koans.05-sets (ns koans.04-sets
(:require [koan-engine.core :refer :all] (:require [koan-engine.core :refer :all]))
[clojure.set :as set]))
(meditations (meditations
"You can create a set by converting another collection" "You can create a set by converting another collection"
@ -12,11 +11,11 @@
"Remember that a set is a *mathematical* set" "Remember that a set is a *mathematical* set"
(= __ (set '(1 1 2 2 3 3 4 4 5 5))) (= __ (set '(1 1 2 2 3 3 4 4 5 5)))
"You can ask Clojure for the union of two sets" "You can ask clojure for the union of two sets"
(= __ (set/union #{1 2 3 4} #{2 3 5})) (= __ (clojure.set/union #{1 2 3 4} #{2 3 5}))
"And also the intersection" "And also the intersection"
(= __ (set/intersection #{1 2 3 4} #{2 3 5})) (= __ (clojure.set/intersection #{1 2 3 4} #{2 3 5}))
"But don't forget about the difference" "But don't forget about the difference"
(= __ (set/difference #{1 2 3 4 5} #{2 3 5}))) (= __ (clojure.set/difference #{1 2 3 4 5} #{2 3 5})))

21
src/koans/06_maps.clj → src/koans/05_maps.clj
View file

@ -1,4 +1,4 @@
(ns koans.06-maps (ns koans.05-maps
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(meditations (meditations
@ -21,7 +21,7 @@
(= __ (:a {:a 1 :b 2})) (= __ (:a {:a 1 :b 2}))
"But map keys need not be keywords" "But map keys need not be keywords"
(= __ ({2010 "Vancouver" 2014 "Sochi" 2018 "PyeongChang"} 2014)) (= __ ({2006 "Torino" 2010 "Vancouver" 2014 "Sochi"} 2010))
"You may not be able to find an entry for a key" "You may not be able to find an entry for a key"
(= __ (get {:a 1 :b 2} :c)) (= __ (get {:a 1 :b 2} :c))
@ -41,23 +41,10 @@
"You can also create a new version with an entry removed" "You can also create a new version with an entry removed"
(= {__ __} (dissoc {1 "January" 2 "February"} 2)) (= {__ __} (dissoc {1 "January" 2 "February"} 2))
"Create a new map by merging"
(= {:a 1 :b 2 __ __} (merge {:a 1 :b 2} {:c 3}))
"Specify how to handle entries with same keys when merging"
(= {:a 1 :b __ :c 3} (merge-with + {:a 1 :b 1} {:b 1 :c 3}))
"Often you will need to get the keys, but the order is undependable" "Often you will need to get the keys, but the order is undependable"
(= (list __ __ __) (= (list __ __ __)
(sort (keys { 2014 "Sochi" 2018 "PyeongChang" 2010 "Vancouver"}))) (sort (keys {2010 "Vancouver" 2014 "Sochi" 2006 "Torino"})))
"You can get the values in a similar way" "You can get the values in a similar way"
(= (list __ __ __) (= (list __ __ __)
(sort (vals {2010 "Vancouver" 2014 "Sochi" 2018 "PyeongChang"}))) (sort (vals {2006 "Torino" 2010 "Vancouver" 2014 "Sochi"}))))
"You can even iterate over the map entries as a seq"
(= {:a __ :b __}
(into {}
(map
(fn [[k v]] [k (inc v)])
{:a 1 :b 2}))))

4
src/koans/07_functions.clj → src/koans/06_functions.clj
View file

@ -1,4 +1,4 @@
(ns koans.07-functions (ns koans.06-functions
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(defn multiply-by-ten [n] (defn multiply-by-ten [n]
@ -23,7 +23,7 @@
(= __ (#(+ %1 %2 %3) 4 5 6)) (= __ (#(+ %1 %2 %3) 4 5 6))
"Arguments can also be skipped" "Arguments can also be skipped"
(= __ (#(str "AA" %2) "bb" "CC")) (= __ (#(* 15 %2) 1 2))
"One function can beget another" "One function can beget another"
(= 9 (((fn [] ___)) 4 5)) (= 9 (((fn [] ___)) 4 5))

22
src/koans/08_conditionals.clj → src/koans/07_conditionals.clj
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@ -1,12 +1,14 @@
(ns koans.08-conditionals (ns koans.07-conditionals
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(defn explain-exercise-velocity [exercise-term] (defn explain-defcon-level [exercise-term]
(case exercise-term (case exercise-term
:bicycling "pretty fast" :fade-out :you-and-what-army
:jogging "not super fast" :double-take :call-me-when-its-important
:walking "not fast at all" :round-house :o-rly
"is that even exercise?")) :fast-pace :thats-pretty-bad
:cocked-pistol :sirens
:say-what?))
(meditations (meditations
"You will face many decisions" "You will face many decisions"
@ -38,10 +40,10 @@
'doom 'doom
'more-doom)) 'more-doom))
"In case of emergency, go fast" "In case of emergency, sound the alarms"
(= "pretty fast" (= :sirens
(explain-exercise-velocity __)) (explain-defcon-level __))
"But admit it when you don't know what to do" "But admit it when you don't know what to do"
(= __ (= __
(explain-exercise-velocity :watching-tv))) (explain-defcon-level :yo-mama)))

2
src/koans/09_higher_order_functions.clj → src/koans/08_higher_order_functions.clj
View file

@ -1,4 +1,4 @@
(ns koans.09-higher-order-functions (ns koans.08-higher-order-functions
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(meditations (meditations

6
src/koans/10_runtime_polymorphism.clj → src/koans/09_runtime_polymorphism.clj
View file

@ -1,4 +1,4 @@
(ns koans.10-runtime-polymorphism (ns koans.09-runtime-polymorphism
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(defn hello (defn hello
@ -6,7 +6,7 @@
([a] (str "Hello, you silly " a ".")) ([a] (str "Hello, you silly " a "."))
([a & more] (str "Hello to this group: " ([a & more] (str "Hello to this group: "
(apply str (apply str
(interpose ", " (cons a more))) (interpose ", " (concat (list a) more)))
"!"))) "!")))
(defmulti diet (fn [x] (:eater x))) (defmulti diet (fn [x] (:eater x)))
@ -31,7 +31,7 @@
"Animals have different names" "Animals have different names"
(= "Thumper eats veggies." (= "Thumper eats veggies."
(diet {:species "rabbit" :name "Thumper" :age 1 :eater :herbivore})) (diet {:species "rabbit" :name "Thumper" :age 1 :eater :herbivore}))
"Different methods are used depending on the dispatch function result" "Different methods are used depending on the dispatch function result"
(= "Simba eats animals." (= "Simba eats animals."

10
src/koans/11_lazy_sequences.clj → src/koans/10_lazy_sequences.clj
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@ -1,4 +1,4 @@
(ns koans.11-lazy-sequences (ns koans.10-lazy-sequences
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(meditations (meditations
@ -17,12 +17,12 @@
(drop __ (range 100))) (drop __ (range 100)))
"Iteration provides an infinite lazy sequence" "Iteration provides an infinite lazy sequence"
(= __ (take 8 (iterate (fn [x] (* x 2)) 1))) (= __ (take 20 (iterate inc 0)))
"Repetition is key" "Repetition is key"
(= [:a :a :a :a :a :a :a :a :a :a] (= [:a :a :a :a :a :a :a :a :a :a ]
(repeat 10 __)) (repeat 10 __))
"Iteration can be used for repetition" "Iteration can be used for repetition"
(= (repeat 100 "hello") (= (repeat 100 :foo)
(take 100 (iterate ___ "hello")))) (take 100 (iterate ___ :foo))))

4
src/koans/12_sequence_comprehensions.clj → src/koans/11_sequence_comprehensions.clj
View file

@ -1,4 +1,4 @@
(ns koans.12-sequence-comprehensions (ns koans.11-sequence-comprehensions
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(meditations (meditations
@ -20,7 +20,7 @@
(for [x __ :when (odd? x)] (for [x __ :when (odd? x)]
x)) x))
"Combinations of these transformations are trivial" "Combinations of these transformations is trivial"
(= '(1 9 25 49 81) (= '(1 9 25 49 81)
(map (fn [x] (* x x)) (map (fn [x] (* x x))
(filter odd? (range 10))) (filter odd? (range 10)))

2
src/koans/13_creating_functions.clj → src/koans/12_creating_functions.clj
View file

@ -1,4 +1,4 @@
(ns koans.13-creating-functions (ns koans.12-creating-functions
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(defn square [x] (* x x)) (defn square [x] (* x x))

8
src/koans/14_recursion.clj → src/koans/13_recursion.clj
View file

@ -1,4 +1,4 @@
(ns koans.14-recursion (ns koans.13-recursion
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(defn is-even? [n] (defn is-even? [n]
@ -33,12 +33,12 @@
(= '(1) (recursive-reverse [1])) (= '(1) (recursive-reverse [1]))
"Yet it becomes more difficult the more steps you take" "Yet it becomes more difficult the more steps you take"
(= '(6 5 4 3 2) (recursive-reverse [2 3 4 5 6])) (= '(5 4 3 2 1) (recursive-reverse [1 2 3 4 5]))
"Simple things may appear simple" "Simple things may appear simple."
(= 1 (factorial 1)) (= 1 (factorial 1))
"They may require other simple steps" "They may require other simple steps."
(= 2 (factorial 2)) (= 2 (factorial 2))
"Sometimes a slightly bigger step is necessary" "Sometimes a slightly bigger step is necessary"

16
src/koans/15_destructuring.clj → src/koans/14_destructuring.clj
View file

@ -1,4 +1,4 @@
(ns koans.15-destructuring (ns koans.14-destructuring
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(def test-address (def test-address
@ -12,16 +12,16 @@
[:foo :bar])) [:foo :bar]))
"Whether in function definitions" "Whether in function definitions"
(= (str "An Oxford comma list of apples, " (= (str "First comes love, "
"oranges, " "then comes marriage, "
"and pears.") "then comes Clojure with the baby carriage")
((fn [[a b c]] __) ((fn [[a b c]] __)
["apples" "oranges" "pears"])) ["love" "marriage" "Clojure"]))
"Or in let expressions" "Or in let expressions"
(= "Rich Hickey aka The Clojurer aka Go Time aka Lambda Guru" (= "Rich Hickey aka The Clojurer aka Go Time aka Macro Killah"
(let [[first-name last-name & aliases] (let [[first-name last-name & aliases]
(list "Rich" "Hickey" "The Clojurer" "Go Time" "Lambda Guru")] (list "Rich" "Hickey" "The Clojurer" "Go Time" "Macro Killah")]
__)) __))
"You can regain the full argument if you like arguing" "You can regain the full argument if you like arguing"
@ -29,7 +29,7 @@
(let [[first-name last-name :as full-name] ["Stephen" "Hawking"]] (let [[first-name last-name :as full-name] ["Stephen" "Hawking"]]
__)) __))
"Break up maps by keys" "Break up maps by key"
(= "123 Test Lane, Testerville, TX" (= "123 Test Lane, Testerville, TX"
(let [{street-address :street-address, city :city, state :state} test-address] (let [{street-address :street-address, city :city, state :state} test-address]
__)) __))

2
src/koans/16_refs.clj → src/koans/15_refs.clj
View file

@ -1,4 +1,4 @@
(ns koans.16-refs (ns koans.15-refs
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(def the-world (ref "hello")) (def the-world (ref "hello"))

2
src/koans/17_atoms.clj → src/koans/16_atoms.clj
View file

@ -1,4 +1,4 @@
(ns koans.17-atoms (ns koans.16-atoms
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(def atomic-clock (atom 0)) (def atomic-clock (atom 0))

22
src/koans/24_macros.clj → src/koans/17_macros.clj
View file

@ -1,4 +1,4 @@
(ns koans.24-macros (ns koans.17-macros
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(defmacro hello [x] (defmacro hello [x]
@ -7,23 +7,23 @@
(defmacro infix [form] (defmacro infix [form]
(list (second form) (first form) (nth form 2))) (list (second form) (first form) (nth form 2)))
(defmacro infix-concise [form] (defmacro infix-better [form]
`(~(second form) ; Note the syntax-quote (`) and unquote (~) characters! `(~(second form) ; Note the syntax-quote (`) and unquote (~) characters!
__ __
__)) __ ))
(defmacro recursive-infix [form] (defmacro r-infix [form]
(cond (not (seq? form)) (cond (not (seq? form))
__ __
(= 1 (count form)) (= 1 (count form))
`(recursive-infix ~(first form)) `(r-infix ~(first form))
:else :else
(let [operator (second form) (let [operator (second form)
first-arg (first form) first-arg (first form)
others __] others __]
`(~operator `(~operator
(recursive-infix ~first-arg) (r-infix ~first-arg)
(recursive-infix ~others))))) (r-infix ~others)))))
(meditations (meditations
"Macros are like functions created at compile time" "Macros are like functions created at compile time"
@ -36,10 +36,10 @@
(= __ (macroexpand '(infix (9 + 1)))) (= __ (macroexpand '(infix (9 + 1))))
"You can do better than that - hand crafting FTW!" "You can do better than that - hand crafting FTW!"
(= '(* 10 2) (macroexpand '(infix-concise (10 * 2)))) (= __ (macroexpand '(infix-better (10 * 2))))
"Things don't always work as you would like them to" "Things don't always work as you would like them to... "
(= '(+ 10 (2 * 3)) (macroexpand '(infix-concise (10 + (2 * 3))))) (= __ (macroexpand '(infix-better ( 10 + (2 * 3)))))
"Really, you don't understand recursion until you understand recursion" "Really, you don't understand recursion until you understand recursion"
(= 36 (recursive-infix (10 + (2 * 3) + (4 * 5))))) (= 36 (r-infix (10 + (2 * 3) + (4 * 5)))))

2
src/koans/19_datatypes.clj → src/koans/18_datatypes.clj
View file

@ -1,4 +1,4 @@
(ns koans.19-datatypes (ns koans.18-datatypes
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(defrecord Nobel [prize]) (defrecord Nobel [prize])

25
src/koans/18_quote.clj
View file

@ -1,25 +0,0 @@
(ns koans.18-quote
(:require [koan-engine.core :refer :all]))
(meditations
"Wrap a quote around a list to suppress evaluation"
(= (quote (1 2 3 4 5)) __)
"There is a shortcut too!"
(= (quote __) '(1 2 3 4 5))
"You can quote symbols as well as lists... without evaluation!"
(= __ (let [age 9] (quote age)))
"You can use a literal list as a data collection without having Clojure try to call a function"
(= (cons 1 (__ (2 3))) (list 1 2 3) (cons 1 [2 3]))
"The quote affects all of its arguments, not just the top level"
(= (list 1 __) '(1 (+ 2 3)))
"Syntax-quote (`) acts similarly to the normal quote"
(= (list __ __ __) `(1 2 3) '(1 2 3))
"Unquote (~) within a syntax-quoted expression lets you mark specific expressions as requiring evaluation"
(= (list __ __) `(1 ~(+ 2 3)) '(1 5)))

2
src/koans/20_java_interop.clj → src/koans/19_java_interop.clj
View file

@ -1,4 +1,4 @@
(ns koans.20-java-interop (ns koans.19-java-interop
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(meditations (meditations

8
src/koans/21_partition.clj → src/koans/20_partition.clj
View file

@ -1,4 +1,4 @@
(ns koans.21-partition (ns koans.20-partition
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(meditations (meditations
@ -8,14 +8,14 @@
"But watch out if there are not enough elements to form n sequences" "But watch out if there are not enough elements to form n sequences"
(= '(__) (partition 3 [:a :b :c :d :e])) (= '(__) (partition 3 [:a :b :c :d :e]))
"You can use partition-all to include any leftovers too" "You can use partition-all to also get partitions with less than n elements"
(= __ (partition-all 3 (range 5))) (= __ (partition-all 3 (range 5)))
"If you need to, you can start each sequence with an offset" "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))) (= '((0 1 2) (5 6 7) (10 11 12)) (partition 3 __ (range 13)))
"Consider padding the last sequence with some default values" "Consider padding the last sequence with some default values..."
(= '((0 1 2) (3 4 5) (6 :hello)) (partition 3 3 [__] (range 7))) (= '((0 1 2) (3 4 5) (6 :hello)) (partition 3 3 [__] (range 7)))
"But notice that they will only pad up to the given sequence length" "... but notice that they will only pad up to the given sequence length"
(= '((0 1 2) (3 4 5) __) (partition 3 3 [:these :are "my" "words"] (range 7)))) (= '((0 1 2) (3 4 5) __) (partition 3 3 [:these :are "my" "words"] (range 7))))

16
src/koans/22_group_by.clj → src/koans/21_group_by.clj
View file

@ -1,4 +1,4 @@
(ns koans.22-group-by (ns koans.21-group-by
(:require [koan-engine.core :refer :all])) (:require [koan-engine.core :refer :all]))
(defn get-odds-and-evens [coll] (defn get-odds-and-evens [coll]
@ -6,9 +6,11 @@
[odds evens])) [odds evens]))
(meditations (meditations
"To categorize a collection by some function, use group-by"
"To categorize a collection by some function, use group-by."
(= __ (group-by count ["hello" "world" "foo" "bar"])) (= __ (group-by count ["hello" "world" "foo" "bar"]))
"You can simulate filter + remove in one pass" "You can simulate filter + remove in one pass"
(= (get-odds-and-evens [1 2 3 4 5]) (= (get-odds-and-evens [1 2 3 4 5])
((juxt filter remove) odd? [1 2 3 4 5]) ((juxt filter remove) odd? [1 2 3 4 5])
@ -17,20 +19,20 @@
"You can also group by a primary key" "You can also group by a primary key"
(= __ (= __
(group-by :id [{:id 1 :name "Bob"} (group-by :id [{:id 1 :name "Bob"}
{:id 2 :name "Jennifer"} {:id 2 :name "Mike"}
{:id 1 :last-name "Smith"} ])) {:id 1 :last-name "Smith"} ]))
"But be careful when you group by a non-required key" "But be careful when you group by non-required key"
(= {"Bob" [{:name "Bob" :id 1}] (= {"Bob" [{:name "Bob" :id 1}]
"Jennifer" [{:name "Jennifer" :id 2}] "Mike" [{:name "Mike" :id 2}]
__ [{:last-name "Smith" :id 1}]} __ [{:last-name "Smith" :id 1}]}
(group-by :name [{:id 1 :name "Bob"} (group-by :name [{:id 1 :name "Bob"}
{:id 2 :name "Jennifer"} {:id 2 :name "Mike"}
{:id 1 :last-name "Smith"}])) {:id 1 :last-name "Smith"}]))
"The true power of group-by comes with custom functions" "The true power of group-by comes with custom functions"
(= __ (= __
(group-by #(if (:bad %) :naughty-list :nice-list) (group-by #(if (:bad %) :naughty-list :nice-list)
[{:name "Jimmy" :bad true} [{:name "Jimmy" :bad true}
{:name "Jane" :bad false} {:name "Jack" :bad false}
{:name "Joe" :bad true}]))) {:name "Joe" :bad true}])))

51
src/koans/23_meta.clj
View file

@ -1,51 +0,0 @@
(ns koans.23-meta
(:require [koan-engine.core :refer :all]))
(def giants
(with-meta 'Giants
{:league "National League"}))
(meditations
"Some objects can be tagged using the with-meta function"
(= __ (meta giants))
"Or more succinctly with a reader macro"
(= __ (meta '^{:division "West"} Giants))
"While others can't"
(= __ (try
(with-meta
2
{:prime true})
(catch ClassCastException e
"This doesn't implement the IObj interface")))
"Notice when metadata carries over"
(= __ (meta (merge '^{:foo :bar} {:a 1 :b 2}
{:b 3 :c 4})))
"And when it doesn't"
(= __ (meta (merge {:a 1 :b 2}
'^{:foo :bar} {:b 3 :c 4})))
"Metadata can be used as a type hint to avoid reflection during runtime"
(= __ (#(.charAt ^String % 0) "Cast me"))
"You can directly update an object's metadata"
(= 8 (let [giants
(with-meta
'Giants
{:world-series-titles (atom 7)})]
(swap! (:world-series-titles (meta giants)) __)
@(:world-series-titles (meta giants))))
"You can also create a new object from another object with metadata"
(= {:league "National League" :park "Oracle Park"}
(meta (vary-meta giants
assoc __ __)))
"But it won't affect behavior like equality"
(= __ (vary-meta giants dissoc :league))
"Or the object's printed representation"
(= __ (pr-str (vary-meta giants dissoc :league))))

66
src/koans/25_threading_macros.clj
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@ -1,66 +0,0 @@
(ns koans.25-threading-macros
(:require [koan-engine.core :refer :all]))
(def a-list
'(1 2 3 4 5))
(def a-list-with-maps
'({:a 1} {:a 2} {:a 3}))
(defn function-that-takes-a-map [map a b]
(get map :a))
(defn function-that-takes-a-coll [a b coll]
(map :a coll))
(meditations
"We can use thread first for more readable sequential operations"
(= __
(-> {}
(assoc :a 1)))
"Consider also the case of strings"
(= __
(-> "Hello world"
(str ", and moon")
(str ", and stars")))
"When a function has no arguments to partially apply, just reference it"
(= __
(-> "String with a trailing space "
clojure.string/trim))
"Most operations that take a scalar value as an argument can be threaded-first"
(= __
(-> {}
(assoc :a 1)
(assoc :b 2)
(assoc :c {:d 4
:e 5})
(update-in [:c :e] inc)
(get-in [:c :e])))
"We can use functions we have written ourselves that follow this pattern"
(= __
(-> {}
(assoc :a 1)
(function-that-takes-a-map "hello" "there")))
"We can also thread last using ->>"
(= __
(->> [1 2 3]
(map inc)))
"Most operations that take a collection can be threaded-last"
(= __
(->> a-list
(map inc)
(filter even?)
(into [])
(reduce +)))
"We can use functions we have written ourselves that follow this pattern"
(= __
(->> a-list-with-maps
(function-that-takes-a-coll "hello" "there")
(into []))))

30
src/koans/26_transducers.clj
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@ -1,30 +0,0 @@
(ns koans.26-transducers
(:require [koan-engine.core :refer :all]))
(def example-transducer
(map inc))
(def transforms
(comp (map inc)
(filter even?)))
(meditations
"A sequence operation with only one argument often returns a transducer"
(= __
(sequence example-transducer [1 2 3]))
"Consider that sequence operations can be composed as transducers"
(= __
(transduce transforms conj [1 2 3]))
"We can do this eagerly"
(= __
(into [] transforms [1 2 3]))
"Or lazily"
(= __
(sequence transforms [1 2 3]))
"The transduce function can combine mapping and reduction"
(= __
(transduce transforms + [1 2 3])))

44
src/koans/27_multimethods.clj
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@ -1,44 +0,0 @@
(ns koans.27-multimethods
(:require [koan-engine.core :refer :all]))
(defmulti multimethod-without-args
(fn [keyword-arg] keyword-arg))
(defmethod multimethod-without-args :first [_]
(str "Hello, World!"))
(defmethod multimethod-without-args :second [_]
(str "Hello there"))
(defmulti multimethod-with-args
(fn [opt-one opt-two] opt-one))
(defmethod multimethod-with-args :path-one [_ opts]
(:first-opt opts))
(defmethod multimethod-with-args :path-two [_ opts]
(let [numbers (:second-opt opts)]
(->> numbers
(map inc)
(reduce +))))
(defmethod multimethod-with-args :path-three [_])
(meditations
"A multimethod takes one or more arguments to dispatch on"
(= __
(multimethod-without-args :first))
"Though it can be ignored and represented by _ in defmethods"
(= __
(multimethod-without-args :second))
"Alternatively, we can use the arguments in defmethods"
(= __
(multimethod-with-args :path-one {:first-opt 1
:second-opt 2}))
"This allows us to do something different in each method implementation"
(= __
(multimethod-with-args :path-two {:first-opt 1
:second-opt [0 1 2]})))