[plt-scheme] HtDP newbie question, 12.4.2

On Mar 27, 2008, at 10:04 PM, Cooke Kelsey wrote:

> Hi, I think I see what you are driving at.
...
> the words are missing the letter A, the first of the current (****)  
> word
...
>  I thought of your reminder to use helper functions, e.g. "add- 
> prefix," but I keep going back to this register idea.  I don't know  
> whether I am getting off track or what.

What would "add-prefix" do? "Register" sounds like an old man's way  
of thinking about machines and lower-level representations of  
computations yet. But add-prefix seems definitely related to the  
"it's missing the letter ..." part.

Where should this missing letter get added in the result of (insert- 
in-single-word s (rest word))? Correct! At the beginning.

Keep going. -- Matthias


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