[racket] arrangements exercise

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Fri Jul 6 08:21:07 EDT 2012

On Jul 6, 2012, at 5:48 AM, Sean Kemplay wrote:

> I am going through htdp first edition (at chapter 17 which refers to arrangements from chapter 12 which is why I revisited the exercise). Would you suggest continuing with this edition or moving to the draft second edition

I would switch to '2e' if I were you. It's more fun but you will learn mostly the same ideas. ('2e' provides an event-driven program context as  playground for developing design skills. '1e' provides no real context.) 

> Do you mean the contract for insert-everywhere/word should be symbol word -> list of words? And will the words returned be the same length? Ie am I aiming for the same result as the current definition?

Letter List-of-Words -> List-of-Words
insert letter l in all positions in all words in lw 

(define (insert-everywhere/all-words l lw) 

Letter Word -> List-of-Words 
insert letter l in all positions in one word (w) 

(define (insert-everywhere/1word l w) 
  (list w))

;; --- 

I recommend you make up examples (with check-expect) first and send them back to the list.
The above 'stub' implementations should fail most of your examples. (A stub/silly/stupid/obviously-wrong
implementation is something '2e' suggests.) 

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