Clojure Koans 2 Strings Notebook

{:hello (clojure-version)}

(ns koans.02-strings

  (:require [clojure.string :as string]))

;; "A string is nothing more than text surrounded by double quotes"

(= (str \h \e \l \l \o) "hello")

;; skill 2001: convert a list of character literals to a string using the `str` function

;; "But double quotes are just magic on top of something deeper"

(= "world" (str 'world))

;; skill 2002: convert a non-string into a string using the `str` function

;; "You can do more than create strings, you can put them together"

(= "Cool right?" (str "Cool " "right?"))

;; skill 2003: concatenate a list of strings into one string using the `str` function

;; "You can even get certain characters"

(= \C (get "Characters" 0))

;; skill 2004: access a character at index X of a string using the `get` function

;; "Or even count the characters"

(= 11 (count "Hello World"))

;; skill 2005: count the # of characters in a string using the `count` function

;; "But strings and characters are not the same"

(= false (= \c "c"))

;; "What if you only wanted to get part of a string?"

(= "World" (subs "Hello World" 6 11))

;; skill 2006: extract a substring from a string using the `subs` function with one input string and two index arguments

;; "How about joining together elements in a list?"

(= "123" (string/join '(1 2 3)))

;; skill 2007: concat list items together into a string using clojure.string/join

;; "What if you wanted to separate them out?"

(= "1, 2, 3" (string/join ", " '(1 2 3)))

;; skill 2008: concat list items together with interleaved (?) inbetween text using clojure.string/join and a string argument

;; "Maybe you want to separate out all your lines"

(= ["1" "2" "3"] (string/split-lines "1\n2\n3"))

;; skill 2009: split a string at new-lines into a vector (?) using clojure.string/split-lines

;; "You may want to make sure your words are backwards"

(= "olleh" (string/reverse "hello"))

;; skill 2010: reverse a string using clojure.string/reverse

;; "Maybe you want to find the index of the first occurrence of a substring"

(= 0 (string/index-of "hello world" "h"))

;; skill 2011: get the first index occurance of a string sequence in a string using clojure.string/index-of

;; "Or maybe the last index of the same"

(= 13 (string/last-index-of "hello world, hello" "hello"))

;; skill 2012: get the last index occurance of a string sequnece in a string using clojure.string/last-index-of

;; "But when something doesn't exist, nothing is found"

(= nil (string/index-of "hello world" "bob"))

;; "Sometimes you don't want whitespace cluttering the front and back"

(= "hello world" (string/trim "  \nhello world \t \n"))

;; skill 2013: remove leading and trailing whitespace from strings by using clojure.string/trim.

;; "You can check if something is a char"

(= true (char? \c))

;; skill 2014: check if something is a char using the `char?` function

;; "Strings are strings"

(= true (string? "sleepy"))

;; skill 2015: check if something is a string using the `string?` function

;; "Some strings may be blank"

(= true (string/blank? ""))

;; skill 2016: check if a string is devoid of non-whitespace using the `blank?` function