Question

Some English words can be played on the keys of a piano, such as “face” or
“baggage”. A piano has keys named a, b, c, d, e, f, g.
Write a Scheme function can-play-word? that consumes a word (a non-empty
string) and produces true or false depending on whether the word can be played
on a piano or not. The only characters that can be played on a piano are lower case
letters. Some English words can be played on the keys of a piano, such as “face” or
“baggage”. A piano has keys named a, b, c, d, e, f, g.
Write a Scheme function can-play-word? that consumes a word (a non-empty
string) and produces true or false depending on whether the word can be played
on a piano or not. The only characters that can be played on a piano are lower case
letters. @Computer Science

Answer 1

o sweet.... we are askin the same question...
feel like we should use remove-all definition but i have no clue how to operate it..

Answer 2

yeah... I have no idea how to do this... not that great in cs.. lol :/

Answer 3

...it's only about an hour till the deadline of this assignment.... i'm dying..

Answer 4

Yeah... I only got the first question. LOL. I'm screwed..

Answer 5

........i cant even say i got the first question cuz i didn't pass the test..... are u in cs 115..?

Answer 6

do i know u....?

Answer 7

yeah.. CS 115. In Lori Case class.... I don't think you know me.. I don't know that many people. LOL

Answer 8

i mean d i know u in person? nm we have different profs.... omg what to do...

Answer 9

No, I don't think you know me in person.. haha.. I just wrote all the design recipe stuff down hoping to get part marks.. I didn't get any of the actual functions itself...

Answer 10

o brilliant idea...... i'll do that immediately.... yeah muz get a 25%+ or it's too bad..

Answer 11

what program r u in?

Answer 12

haha.. yeah.. I just hope to get over 25% in the assignments to get that extra mark. LOL... and I'm in honours math.. hbu?

Answer 13

i already chose my program to be actsci....... and i now regret it a lot.... but i want to stay tho..

Answer 14

ooo actsci... a lot of people are taking that actually.. I'm actually taking MTHEL 131(intro to actuarial practice?) as my elective.. and I don't find it that interesting.. LOL

Answer 15

o i dont even know what that is...... my cousin 's in actsci 3rd yr and i juz wanted to get help from her so i chose the same program.. how i realize how tough it is.....><

Answer 16

now==

Answer 17

haha.. that's why you choose a program that you like and enjoy.. I have to go drop off my algebra assignment due in 30 minutes.. LOL i'll be back soon. xD work on those design recipes! xD

Answer 18

o m g...
i didn't even do my algebra assignment......

Answer 19

i was workin on cs all the time..

Answer 20

.... are you serious? ... wow.. Dx I did algebra first cause I find it easier and much more useful than CS... I hate CS ... don't even know why I have to take it...

Answer 21

...more useful....i much better in algebra than in cs so it doesn't matter if i miss one assignment.... thats why i gave it up..

Answer 22

yeah i don't see the point of taking cs.........i'm terrible at it...........

Answer 23

haha.. me too... I don't understand a thing in CS.. everything the prof says is just alien language to me.. LOL.. gonna go drop off algebra now.. i'll be back soon xD

Answer 24

oo~~ see u soon......
btw i cannot log in to my markus no matter which browser i use now...

Answer 25

o.O ur right... some authorization thing... :s

Answer 26

。。。 what should we do..........

Answer 27

I have no idea... I submitted some of mine already... It's probably cause a lot of people are using it or something.. Just keep trying I guess? :S

Answer 28

。。。 i emailed the ta.

Answer 29

I'm rusty at Scheme, but you should do something like this.

(define (can-play-word? word)
(cond
((empty? word) #t)
((char= (car word) 'a) (can-play-word (cdr word)))
((char= (car word) 'b) (can-play-word (cdr word)))
((char= (car word) 'c) (can-play-word (cdr word)))
((char= (car word) 'd) (can-play-word (cdr word)))
((char= (car word) 'e) (can-play-word (cdr word)))
((char= (car word) 'f) (can-play-word (cdr word)))
((char= (car word) 'g) (can-play-word (cdr word)))
(else #f)))

As I said, it might not be exactly like this. I have no way to test it at the moment, but it should follow this general structure:

Make a cond, ask if the word still has elements, if its empty, it's automatically true.
If the letter you recieve is a, b, c, d, e, f or g, you call the function again and keep trying.
If you recieve anything else, it's automatically false.

Answer 30

Hey... thanks for the reply... an error message appeared when I ran the program..
char=: this function is not defined

Answer 31

yeah i have no clue what does char means.... i know car is first and cdr is rest...

Answer 32

hmm, there should be a function that does what char= is supposed to do, anything you remember that is used to compare two values? Lemme look up online

char means a single character like a, b or c

Answer 33

Oh my bad, it's supposed to be

char=?
not
char=

Answer 34

I wrote a helper function can-play-letter? that determines if a single letter is playable. Then for can-play-word? I said it's either that the string is empty (base case), or the first letter is playable (do a little work) and the rest of the word is playable (recursively reduce it to a smaller problem).

Answer 35

;;wordlist: string -> list-of-symbols
;;Purpose: transform a string to a list
;;Examples:(define (wordlist maryh) => (cons #\m (cons #\a (cons #\r (cons #\y (cons #\h empty)))))

(define (wordlist word)
(string->list word))

;;data analysis:
;; if the word contains only a,b,c,d,e,f,g then produces boolean value true
;; if the word contains letters other than a,b,c,d,e,f,g then produces boolean value false
;;wordtest: string->boolean
;;Purpose: produce boolean value of a word whether it contains only a,b,c,d,e,f,g
;;or it contains letters that are not on the piano keyboard by consuming a string
;;Examples:
;;(check-word "dad") => true
;;(check-word "play") => false

(define (check-word word)
(cond [(equal? (list->string(cons (first (wordlist word)) empty))"a") true]
[(equal? (list->string(cons (first (wordlist word)) empty))"b") true]
[(equal? (list->string(cons (first (wordlist word)) empty))"c") true]
[(equal? (list->string(cons (first (wordlist word)) empty))"d") true]
[(equal? (list->string(cons (first (wordlist word)) empty))"e") true]
[(equal? (list->string(cons (first (wordlist word)) empty))"f") true]
[(equal? (list->string(cons (first (wordlist word)) empty))"g") true]
[else false]))

;;tests
(check-expect (check-word "face") true)
(check-expect (check-word "False") false)

;;data analysis:
;;a wordlist is a helper function that
;;help to convert a sting into a list of word
;;can-play-word?: string -> boolean
;;Purpose: produce boolean value depending on whether or not a word can be played on a piano
;;by consuming a string
;;Examples:
;;(can-play-word? "face") => true
;;(can-play-word? "Dad") => false
;;(can-play-word? "apple") => false
;; (can-play-word? "lee-chin") => false

(define (can-play-word? word)
(cond
[(empty? (wordlist word)) true]
[(check-word word)
(can-play-word? (list->string (rest (wordlist word))))]
[else false]))

Answer 36

Sorry, my Scheme is ancient (R5RS, circa 1997).

(define (can-play-letter? letter)
(and (char>=? letter #\a)
(char<=? letter #\g)))

(define (can-play-word? word)
(or (= (string-length word) 0)
(and (can-play-letter? (string-ref word 0))
(can-play-word? (substring word 1 (string-length word))))))