Week 8: About the String Functions

We had to go through the text ourselves and try out the string functions. I found it challenging as these few weeks we have to compose the codes ourselves.

I firstly practiced with the basic codes in order to revise the following three functions:
1. substring

>(substring "tiffany" 0 4)
tiff

2. string-append

>(string-append "tiffany" "is" "a" "good" "girl")
tiffanyisagoodgirl

3. string-length

>(string-length "tiffany")
7

I started working on the tutorial handout afterwards. These are what I got after spending more than an hour on DrRacket.

(define (repeat word)(string-append word word))  

(define (chop-first-char xxx)(substring xxx 1)) 

(define (first-char x)(substring x 0 1)) 

(define (last-half xxxx)(substring xxxx
                                   (round (* 1/2 (string-length xxxx)))))
                                     
(define (first-half xxxx)(substring xxxx 0
                                   (round (* 1/2 (string-length xxxx)))))

these are the outputs:

>(repeat word "tiff")
tifftiff 

>(chop-first-char "tiff")
iff

>(first-char "tiff")
t 

>(last-half "tiff")
ff 

>(first-half "tifff")
ti

This exercise indeed required me think a lot and undoubtedly, a complete understanding of the codes.