Re: Page 76 of OCaml by John Whitington ???

Ok, I agree, but you can simplify your pattern matching of the second part... I'm guessing what you meant to write was:

let rec practice_function list = match list with|[ ] -> false| head :: tail -> match tail with|[ ] -> false|headOfTail :: tailOfTail -> if head = headOfTail then true else practice_function tail ;;

You could just write | [] | head::[] -> false | headOf...Chaining multiple patterns together tells the compiler to map the same action to the same clause.

I can't really understand your intentions with the headOfTail :: tailOfTail part, but it seems you are testing head= headOfTail, which can also be simplified if the overall behavior of the function is to be retained with this, supposing you use what I gave above also.

| head::second::remaining -> if head = second then ...


 

    On Tuesday, March 29, 2016 11:17 AM, "Douglas Lewit [email protected] [ocaml_beginners]" <[email protected]> wrote:
 

     Yes, tailOfTail is a list, but headOfTail is an element ( which could be a list if we're dealing with a list of lists ).
So if I have something like:
let rec practice_function list = match list with|[ ] -> falsehead :: tail -> match tail with|[ ] -> false|headOfTail :: tailOfTail -> if head = headOfTail then true else practice_function tail ;;
I should think that the above function would test the list for equal elements that are right next to each other in the list.  I was trying to base my packing function on similar logic, but my approach became horribly convoluted and it just didn't work.  I think my logic is sound, but my implementation was not effective.
On Tue, Mar 29, 2016 at 3:18 AM, 'Mr. Herr' [email protected] [ocaml_beginners] <[email protected]> wrote:

      
 
 On 29.03.2016 06:41, Douglas Lewit [email protected] [ocaml_beginners] wrote:
  
    I also gave something like this a try, but I ended up with a couple of error messages: 
  let pack list = match list with |[ ] -> [ ] |head :: tail -> match tail with |[ ] -> [ ] headOfTail :: tailOfTail -> if head = headOfTail then..... ( more code ) 
  I thought it was clever, but either I just ended up with an empty list, a one-element list, or the compiler just rejected it.  I'm starting to feel a little dumb!  But I'll keep at it. 
   
 tailOfTail is a list, not an element!
 
 /Str.
    

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