Strings

#Creating a string

To form a string, wrap the characters in double quotes ""

here are some examples of strings:

"hello world"
"why do ants never get sick? because of their anty bodies"
"こんにちは世界" ; hello world in japanese

#What are strings?

A collection of characters to that can represent words, usernames and general text

#What is the difference between the number 123 and the string “123”?

; as you can see they are highlighted differently
123 ; the number 123
"123" ; the string 123

The number 123 can be divided, sqrt, multipled, all the classical math operations you are familar with.
The string "123" is for only for show.

If you try that on the string "123", it will give you an error.

(+ "123" 1)
; ERROR: + execpts a number and not a string.

#Operations on strings

There are operations you can do on a string, like:
string-append , string-length , string->number

; combining two strings with (string-append)
(string-append "123" "1") ; gives "1231"
(string-append "Good morning" "bob") ; gives "Good morningbob"

; convert a string to a number
(string->number "12")
; the other way around is useful when you want to perform
; some calculations on a number, then spit it back out as a string
; 2000mah phone battery
(string-append "You have " (number->string (* (/ 163 2000) 100) " gold") ; gives "You have 8.15% battery"

; get the lengh of a string
(string-length "jest") ; gives 4
(string-length "amazing") ; gives 7

#Zero based indexing

And you can also substring, which gets parts of a string out, though be warned that counting starts from 0.

; [inclusive, exclusive)
;           0123456789
(substring "hello cat" 0 4) ; gives "hello"
; note that the first character is h is 0
(substring "hello cat" 0 1) ; gives "h"

(substring "hello cat" 4 7) ; gives "h"
; string-length however counts normally
(string-length "hello cat") ; gives 9
; how do you get the last character t?
(substring "hello cat" 8) ; gives t, notice it's not 9

This takes some getting used to and has been the cause of numerous security holes in other programming languages. Get some practice with them!

What is (substring "barnicales" 0 5)?

#Practice Problems

Zero based indexing practice

#Videos

Zero based Indexing Video