[plt-scheme] HTDP 12.4.2

OOOPS I am so sorry: the last line should be

  [else (????? (iE/word letter (first alow)) (iE letter (rest alow))]

-- Matthias


On Jun 22, 2006, at 2:31 PM, Matthias Felleisen wrote:

> You have changed the specs on us :-)
>
> On Jun 22, 2006, at 2:06 PM, wooks wooks wrote:
>
>>
>> At 4:43 AM +0100 6/22/06, wooks wooks wrote:
>>> LOL. Ok I've been rumbled.
>>
>> Gee, I hope not :-)
>>
>>> I'll start all over again the way I've been told and await the light 
>>> bulb moment.
>>
>> "Awaiting the light bulb moment" is what you've BEEN doing; we 
>> suggest instead following a systematic procedure that doesn't rely on 
>> unpredictable light bulbs.
>> --
>>
>> I meant the light bulb moment as in true understanding why one should 
>> stick to the systematic procedure (something more than thats how they 
>> told me to do it).
>>
>> Anyway I'd appreciate some input on this revised effort (most 
>> particularly my template) before going to the next stage.
>>
>> ;CONTRACT
>> ;insertEverywhere : symbol ('a - 'z) list-of-words - list of words
>> ;returns a list of words constructed by interpersing symbol before, 
>> after and between each letter, of
>> ;each word in the list-of-words
>> ;
>> ;EXAMPLES
>> ;(insertEverywhere 'd
>> ;  (cons (cons 'e (cons 'r empty))
>> ;    (cons (cons 'r (cons 'e empty))
>> ;      empty))) gives
>> ; (list (list 'd 'e 'r)
>> ;       (list 'e 'd 'r)
>> ;       (list 'e 'r 'd)
>> ;       (list 'd 'r 'e)
>> ;       (list 'r 'd 'e)
>> ;       (list 'r 'e 'd))
>>
>> ;TEMPLATE
>> ;(define (insertEverywhere sym alow)
>> ;  (cond
>> ;    [(empty? alow) ...sym....]
>> ;    [else ...sym...(first (first alow)) .....
>> ;          ..sym....(rest (first alow)) .....
>> ;          .....(insertEverywhere sym (rest alow)).....]
>> ;   )
>> ;)
>
> Good. The rest (no pun intended) is obvious for this one:
>
> (define (iE letter alow)
>   (cond [(empty? alow) empty]
>         [else (??????? (iE/word letter alow) (iE letter (rest alow))]))
>
> iE/word is an entry on your wish list:
>
> ;; iE/word : letter word -> list-of-words
> ;; insert a letter at beginning, end, and between the letters of a word
>
> ????? is up to you. --- Matthias
>
>
>
>
>
>>
>>
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