[racket] how must I interpreted this exercise

Nope, I think I have to read the whole book to get this kind of problems.
First a lot of things to learn as lists, quote/unquote, lamba.

Roelof



Op 25-6-2012 16:14, Matthias Felleisen schreef:
> This is not this kind of problem.
>
>
> On Jun 25, 2012, at 10:06 AM, Richard Cleis wrote:
>
>> 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.
>>>>>
>>>
>>
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