## Function to "push" a list to the right or left

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zcohen
Posts: 6
Joined: Wed Jun 06, 2012 12:41 am

### Function to "push" a list to the right or left

Hi everybody,
I have to write a function that (push-left (L)) "pushes" a list to thr right or to the left.

For example:
(push-left '(1 2 3 4)) will give (2 3 4 1)
(push-right'(1 2 3 4)) will give (4 1 2 3)

The lecturer said we can't use functions 'last' or 'butlast'.
I tried to solve it with no success. Can you give me direction? Is there a way to solve it by recursion?

I thought to simply do this: (cons (rest L) (first L)), but it gives (rest L) as a list. Is there a way to "unlist" it?

Thanks,
Zevi

gugamilare
Posts: 406
Joined: Sat Mar 07, 2009 6:17 pm
Location: Brazil
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### Re: Function to "push" a list to the right or left

Try using the function append