[racket] how must I interpreted this exercise

That is-near a better solution ;o) 

I think HtDP has problems that require assembling sentences from different parts of speech. That is a very challenging software field.

rac
 


On Jun 25, 2012, at 12:41 AM, Roelof Wobben wrote:

> You mean something like this :
> 
> (check-expect (calculate 0 3) 3)
> (define (calculate getal1 getal2)
>  (cond
>    [ (equal? getal1 0) getal2]
>    [ (equal? getal2 0) getal1]
>    [else (sqrt (+ (* getal1 getal1) (* getal2 getal2)))]
>    ))
> 
> ; String -> String
> ; This function produces a string depending on the input "niet " or ""
> (check-expect (afdrukken "") "Het ingegeven punt is dichtbij het 0 punt")
> (check-expect (afdrukken "niet ") "Het ingegeven punt is niet dichtbij het 0 punt")
> (define (afdrukken s)
>  (string-append first_tekst s middle_tekst)
>  )
> 
> 
> ; Struct -> String
> ; Function who outputs "niet" or a empty string depending on the calculated distance compared with R.
> (check-expect (is-near (make-posn 1 0) 5) "Het ingegeven punt is dichtbij het 0 punt")
> (check-expect (is-near (make-posn 3 4)  5) "Het ingegeven punt is niet dichtbij het 0 punt")
> (define (is-near s r)
>  ( if (< (calculate (posn-x s) (posn-y s)) r) (afdrukken "") (afdrukken "niet ")
>       ))
> 
> 
> Roelof
> 
> 
> 
> Op 25-6-2012 6:18, Richard Cleis schreef:
>> Check-expect is used to test your function.
>> Make that work first.
>> 
>> Then you can use the design recipe to make a new function.
>> 
>> The new function will accept the output of your first function and return the message that you want… without any repeated words in the function.
>> 
>> rac
>> 
>> On Jun 24, 2012, at 1:43 PM, Roelof Wobben wrote:
>> 
>>> Hello,
>>> 
>>> This soluation is not what I was looking for.
>>> And it uses list which I don't have learned so far.
>>> 
>>> So far I have this :
>>> 
>>> ; constanten
>>> 
>>> (define R 5)
>>> (define first_tekst "Het ingegeven punt")
>>> (define is_tekst "is")
>>> (define middle_tekst "dichtbij het 0 nulpunt")
>>> (define niet "niet")
>>> 
>>> 
>>> ;Number Number -> Number
>>> ;This function calculates the distance of a given point compared to the origin
>>> (check-expect (calculate 1 0) 1)
>>> (check-expect (calculate 3 4) 5)
>>> (check-expect (calculate 0 3) 3)
>>> (define (calculate getal1 getal2)
>>>   (cond
>>>     [ (equal? getal1 0) getal2]
>>>     [ (equal? getal2 0) getal1]
>>>     [else (sqrt (+ (* getal1 getal1) (* getal2 getal2)))]
>>>     ))
>>> 
>>> ; Struct -> String
>>> ; Function who outputs a string dependinh on the outcome of the calculation of the distance to the origin
>>> (check-expect (is-near (make-s 1 0) "Het ingegeven punt is dichtbij het nulpunt"))
>>> (check-expect (is-near (make-s 3 4) "Het ingeven punt is niet dichtbij het nulpunt"))
>>> (define (is-near s r)
>>>   ( if (< (calculate (posn-x s) (posn-y s)) r)
>>>               
>>> Now I can do  (string append  first_tekst is middle-tekst) and (string-append first-tekst  is niet middle-tekst)  but then I do almost two times the same with one difference the niet part.
>>> And Im looking for a better solution.
>>> 
> 
>