str

user=> "some string"
"some string"

user=> (str)
""

user=> (str nil)
""

user=> (str 1)
"1"

user=> (str 1 2 3)
"123"

user=> (str 1 'symbol :keyword)
"1symbol:keyword"

;; A very common usage of str is to apply it to an existing collection:
user=> (apply str [1 2 3])
"123"

;; compare it with:
user=> (str [1 2 3])
"[1 2 3]"

;; Destructuring with a string, getting just a few characters from it
user=> (let [[first-char second-char] "abcde"] 
         (prn 'first= first-char) 
         (prn 'second= second-char))
first= \a
second= \b
nil

;; More destructuring with a string
user=> (let [[first-char second-char & rest-of-chars] "abcde"] 
         (prn 'first= first-char) 
         (prn 'second= second-char) 
         (prn 'rest= rest-of-chars))
first= \a
second= \b
rest= (\c \d \e)
nil

;; Destructuring, getting the first character of a string
;; and then a reference to the entire string
user=> (let [[first-char :as all-the-string] "abcde"] 
         (prn 'first= first-char) 
         (prn 'all= all-the-string))
first= \a
all= "abcde"
nil

user=> (str "L" "a")
"La"

user=> (str "L" 5 "a")
"L5a"

;; sometimes when printing lazy sequences you do not get what you want.
(str (take 5 (range 10)))
;=> "clojure.lang.LazySeq@1b554e1"

;; in those cases `pr-str` to the rescue.
(pr-str (take 5 (range 10)))
;=> "(0 1 2 3 4)"

;; be careful with java.lang.Double to java.lang.String conversion
(str -128004972.0)
;=> "-1.28004972E8"

;; Using str in maps
(def user-map {:fname "Jane" :sname "Doe"})

;;getting the value of the first key 
(:fname user-map)
;=> "Jane"

(str (:fname user-map) " " (:sname user-map))
;=> "Jane Doe"

(str nil)
;; => ""

(str true)
;; => "true"

(str false)
;; => "false"