[plt-scheme] HTDP 12.4.2

Much easier. Put (first word) back on.

On Jun 23, 2006, at 6:21 PM, wooks wooks wrote:

>
>
> The only thing I can see is that (first word) is not being used but I 
> can't see where to slot it.
> My best idea yet is another auxiliary function to collate all 
> substrings of word that start from the beginnig of word and to merge 
> that with the output I am getting below.
>
>
>
> ----Original Message Follows----
> From: Matthias Felleisen <matthias at ccs.neu.edu>
> To: "wooks wooks" <wookiz at hotmail.com>
> CC: plt-scheme at list.cs.brown.edu
> Subject: Re: [plt-scheme] HTDP 12.4.2
> Date: Fri, 23 Jun 2006 15:15:08 -0400
>
>
> On Jun 23, 2006, at 3:05 PM, wooks wooks wrote:
>
>> (interperse 'f (list 'd 'a 'r 'k))
>>
>> gives
>>
>> (list (list 'f 'd 'a 'r 'k) (list 'f 'a 'r 'k) (list 'f 'r 'k) (list 
>> 'f 'k) 'f)
>>
>> and I want
>>
>> (list (list 'f 'd 'a 'r 'k) (list 'd 'f 'a 'r 'k) (list 'd 'a 'f 'r 
>> 'k) (list 'd 'a 'r 'f 'k) (list 'd 'a 'r 'k 'f))
>
> Change the formating of the two things and take a close look:
>
> (list (list 'f 'd 'a 'r 'k) (list 'f 'a 'r 'k)    (list 'f 'r 'k)      
>  (list 'f 'k)                            'f)
> (list (list 'f 'd 'a 'r 'k) (list 'd 'f 'a 'r 'k) (list 'd 'a 'f 'r 
> 'k) (list 'd 'a 'r 'f 'k) (list 'd 'a 'r 'k 'f))
>
> When you recur with (rest word) you are dropping the first letter, at 
> each stage.  So not surprisingly, the prefix is lost.
>
> Try with an example of length two and see whether you can come up with 
> a better idea.
>
>