Clojure 学习入门（4）—— 字符串

user=> 
user=> (str 1)
"1"
user=> (str -2.5)
"-2.5"
user=> (str "a")
"a"
user=> (str "abc" 123)
"abc123"
user=> (str)
""
user=> (str '(1 2 3))
"(1 2 3)"
user=> (str nil)
""
user=> (str null)
java.lang.Exception: Unable to resolve symbol: null in this context (NO_SOURCE_FILE:149)
user=> (str "null")
"null"
user=> (str "abc " 123)
"abc 123"
user=> (str 123 345)
"123345"

user=> (print-str "abc" 234)
"abc 234"
user=> (println-str "abc" 234)
"abc 234\n"
user=> (pr-str "abc" 234)
"\"abc\" 234"
user=> (prn-str "abc" 234)
"\"abc\" 234\n"
user=> (with-out-str "abc" 234)
""

user=> (count)
java.lang.IllegalArgumentException: Wrong number of args (0) passed to: core$count (NO_SOURCE_FILE:175)
user=> (count nil)
0
user=> (count "abc123")
6

user=> (subs "ithomer" 1)
"thomer"
user=> (subs "ithomer" 1 3)
"th"
user=> (subs "ithomer" 1 (count "ithomer"))
"thomer"
user=> (subs "ithomer" 1 20)
java.lang.StringIndexOutOfBoundsException: String index out of range: 20 (NO_SOURCE_FILE:0)
user=> (subs "ithomer")
java.lang.IllegalArgumentException: Wrong number of args (1) passed to: core$subs (NO_SOURCE_FILE:0)

user=> (format "hello %s" "ithomer.net")
"hello ithomer.net"
user=> (format "%5d" 3)
"    3"
user=> (format "%-5d" 3)
"3    "
user=> (format "%05d" 3)
"00003"

user=> (string? "abc")
true
user=> (string? "123")
true
user=> (string? 123)
false
user=> (string? nil)
false

user=> (char? "abc")
false
user=> (char? \a)
true
user=> (char? 'a')
java.lang.Exception: Unmatched delimiter: )
user=> (char? a)
java.lang.Exception: Unable to resolve symbol: a in this context (NO_SOURCE_FILE:222)
user=> (char? 1)
false
user=> (char? \1)
true
user=> (char? nil)
false