1.(string? v) → boolean?
Returns #t if v is a string, #f otherwise.
(string? "Apple")
#t
(string? 'apple)
#f
(string? 3)
#f
(string? #f)
#f
2.(substring str start [end]) → string?
Index counts from 0.
start parameter position is included.
If end parameter is presented, (end - 1) index position is included.
Without end parameter, it will cut the string to the end.
0 1 2 3 4
A p p l e
(substring "Apple" 1 3)
"pp"
(substring "Apple" 1)
"pple"
3.(string-append str0 str1 str2 ...) → string?
strX : string?
Append str0 str1 str2.... strN together.
(string-append "Apple" "Banana")
"AppleBanana"
(string-append "Apple" "Banana" "cookie")
"AppleBananaCookie"
4.(string=? str1 str2 ...) → boolean?
Returns #t if all of the arguments are equal?
(string=? "Apple" "Apple")
#t
(string=? "Apple" "apple")
#f
(string=? "a" "as" "a")
#f
5.(string-length str) → exact-nonnegative-integer?
str : string?
Returns the length of str.
(string-length "Apple")
5