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Things with Strings

Scheme symbols are normally case-insensitive. Thus the symbols Maya and maya  are identical:

(eqv? 'Maya 'maya)
;Value: #t

;We can now use the symbol Maya as a global variable by using the form "define"
(define Maya 10)
;Value: maya

Maya
;Value: 10

maya
;Value: 10

;You see it again - not case-sensitive!

;Changing the value of a global variable is very easy. We use set! for the modification.
(set! maya 12)
;Value: 10

Maya
;Value: 12

maya
;Value: 12

 

;Working with strings. Simply a string is nothing but a combination of atoms.
(define setofatoms "Hello")
;Value: setofatoms

setofatoms
;Value 11: "Hello"

;Accessing the atoms of a given string
(string-ref setofatoms 0)
;Value: #\H

(string-ref setofatoms 1)
;Value: #\e

;Predicate for checking stringness:
(string? setofatoms)
;Value: #t

;But whow long is a given string. The answer give us:
(string-length setofatoms)
;Value: 5

; A function for splitting a given string

(define (splittmyatom mystring i)
 (if (< i (string-length mystring))
     (begin
       (display "; #")
       (display i)
       (display ": ")
       (display (string-ref mystring i))
       (newline)
       (splittmyatom mystring (+ i 1))
        )
     #t))
;Value: splittmyatom

(splittmyatom "Hallo" 0)
; #0: H
; #1: a
; #2: l
; #3: l
; #4: o
;Value: #t

 

; Appending new strings
(string-append "H" "A" "LLo")
;Value 13: "HALLo"

; Mod a string
(define mystring "Hallo")
;Value: mystring

mystring
;Value 14: "Hallo"

(string-set! mystring 1 #\e)
;Unspecified return value

mystring
;Value 14: "Hello"

; Et voilà: Hallo changed to hello.

 

 

25. März 2019     | mit scheme | scheme | lisp | old data

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