dariooddenino / examples

Clojure examples in the REPL

examples

Clojure examples from clojuredocs.org for when doc is not enough!

Usage

Installation

• Add the dependency to your project:

(defproject ...
    :dependencies [[examples "0.3.0"]]}

• And require it:

(:require [examples.core :refer [examples clear-examples-cache])

Printing examples

(examples [fun])

E.g. (examples map) will print all clojuredocs.org examples of map:

-----------------------------------------------
clojure.core/map
-----------------------------------------------
(map inc [1 2 3 4 5])
;;=> (2 3 4 5 6)


;; map can be used with multiple collections. Collections will be consumed
;; and passed to the mapping function in parallel:
(map + [1 2 3] [4 5 6])
;;=> (5 7 9)


;; When map is passed more than one collection, the mapping function will
;; be applied until one of the collections runs out:
(map + [1 2 3] (iterate inc 1))
;;=> (2 4 6)



;; map is often used in conjunction with the # reader macro:
(map #(str "Hello " % "!" ) ["Ford" "Arthur" "Tricia"])
;;=> ("Hello Ford!" "Hello Arthur!" "Hello Tricia!")

;; A useful idiom to pull "columns" out of a collection of collections. 
;; Note, it is equivalent to:
;; user=> (map vector [:a :b :c] [:d :e :f] [:g :h :i])

(apply map vector [[:a :b :c]
                   [:d :e :f]
                   [:g :h :i]])

;;=> ([:a :d :g] [:b :e :h] [:c :f :i])

;; From http://clojure-examples.appspot.com/clojure.core/map

-----------

user=> (map #(vector (first %) (* 2 (second %)))
            {:a 1 :b 2 :c 3})
([:a 2] [:b 4] [:c 6])

user=> (into {} *1)
{:a 2, :b 4, :c 6}

-----------

;; Use a hash-map as a function to translate values in a collection from the 
;; given key to the associated value

user=> (map {2 "two" 3 "three"} [5 3 2])
(nil "three" "two")

;; then use (filter identity... to remove the nils
user=> (filter identity (map {2 "two" 3 "three"} [5 3 2]))
("three" "two")

-----------

;; mapping over a hash-map applies (into) first. 
;; need to use functions that deal with arrays (fn [[key val]] ...)
(map pprint {:key :val :key1 :val1})
([:key :val]
[:key1 :val1]
nil nil)

;;above, the pprint output appears to be part of the return value but it's not:
(hash-set (map pprint {:key :val :key1 :val1}))
[:key :val]
[:key1 :val1]
#{(nil nil)}

(map second {:key :val :key1 :val1})
(:val :val1)

-----------

(map fn [a 4 x]
        [b 5 y]
        [c 6])    
;        ^ ^
; applies fn to a b c as (fn a b c)
; applies fn to 4 5 6 as (fn 4 5 6)
; ignores (x y)
; returns a list of results
; equivalent to (list (fn a b c) (fn 4 5 6))

;example
(map list [1 2 3]
         '(a b c)
         '(4 5))

user=> (map list  [1 2 3] '(a b c) '(4 5))
((1 a 4) (2 b 5))
;same as
user=> (list (list 1 'a 4) (list 2 'b 5))
((1 a 4) (2 b 5))

-----------

; map passed two collection arguments. From 4Clojure Problem #157

(def d1 [:a :b :c])
(#(map list % (range)) d1)
;;=> ((:a 0) (:b 1) (:c 2))

-----------

;; Used without a collection, map will create a transducer:
(def xf (map inc))

;; We can now apply this transducer to a sequence:
(transduce xf conj (range 5))
;; => [1 2 3 4 5]

-----------

;; Extract keyword from a collection of obj
(map :a '({:a 1 :b 0} {:a 2 :b 0} {:a 3 :b 1} {:a 3 :b 0}))
;; =>(1 2 3 3)

-----------

Clearing cache

Cache can be cleared with (clear-examples-cache [fun]). If fun is omitted, the entire cache will be cleared.

License

Copyright © 2016 Dario Oddenino

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.

examples's Issues

Behaviour should be to print string, not to return it

Hey, if you're looking at the behaviour of #'doc or #'source you see that they actually print the result, as opposed to just returning it. Based on your use case, I think your library should do the same thing!H