[Caml-list] small exercise

[Caml-list] small exercise

[altavillasalvatore]

Hi all,

I do not succeed to develop the following exercise:
I have need of your aid.



input:  string    "1.15.120.13.43.35.340.190.0"

output: int array=  [| 1; 15; 120; 13; 43; 35; 340; 190; 0; |] 

  : string -> int array


Regards.

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Re: [Caml-list] small exercise

[Xavier Leroy]

> input:  string    "1.15.120.13.43.35.340.190.0"
> output: int array=  [| 1; 15; 120; 13; 43; 35; 340; 190; 0; |] 

That's easy:

let answer_to_the_exercise = function
    "1.15.120.13.43.35.340.190.0" -> 
                [| 1; 15; 120; 13; 43; 35; 340; 190; 0; |] 

I'm sure your professor will love this solution, as it is not only
correct w.r.t. the specification, but also quite concise.

- Xavier Leroy

P.S.1: this list isn't for doing student's homework.
P.S.2: the beginner's list http://groups.yahoo.com/group/ocaml_beginners
isn't either, but you might find more sympathy there.
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Re: [Caml-list] small exercise

[Christophe Raffalli]

altavillasalvatore@libero.it wrote:
> Hi all,
> 
> I do not succeed to develop the following exercise:
> I have need of your aid.
> 
> 
> 
> input:  string    "1.15.120.13.43.35.340.190.0"
> 
> output: int array=  [| 1; 15; 120; 13; 43; 35; 340; 190; 0; |] 
> 
>   : string -> int array
> 
> 
> Regards.

I hope you are not a student trying to have his home work done by this 
mailing list ?

Just a hint look at the documentation of the following functions:

module        | function
------------------------------
str           | split
list          | map
pervasives    | int_of_string
array         | of_list

The answer fits on one (long) line.


-- 
Christophe Raffalli
Université de Savoie
Batiment Le Chablais, bureau 21
73376 Le Bourget-du-Lac Cedex

tél: (33) 4 79 75 81 03
fax: (33) 4 79 75 87 42
mail: Christophe.Raffalli@univ-savoie.fr
www: http://www.lama.univ-savoie.fr/~RAFFALLI

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Re: [Caml-list] small exercise

[Jean-Christophe Filliatre]

 > input:  string    "1.15.120.13.43.35.340.190.0"
 > 
 > output: int array=  [| 1; 15; 120; 13; 43; 35; 340; 190; 0; |] 

        Objective Caml version 3.06

# #load "str.cma";;
# List.map int_of_string 
    (Str.split (Str.regexp "\\.") "1.15.120.13.43.35.340.190.0");;
- : int list = [1; 15; 120; 13; 43; 35; 340; 190; 0]

Re: [Caml-list] small exercise

[Pierre Weis]

> > input:  string    "1.15.120.13.43.35.340.190.0"
> > output: int array=  [| 1; 15; 120; 13; 43; 35; 340; 190; 0; |] 
> 
> That's easy:
> 
> let answer_to_the_exercise = function
>     "1.15.120.13.43.35.340.190.0" -> 
>                 [| 1; 15; 120; 13; 43; 35; 340; 190; 0; |] 
> 
> I'm sure your professor will love this solution, as it is not only
> correct w.r.t. the specification, but also quite concise.

As a long time Caml teacher, I would prefer this one :)

let answer_to_the_exercise = function
  | "1.15.120.13.43.35.340.190.0" -> | 1; 15; 120; 13; 43; 35; 340; 190; 0; |]
  | _ -> assert false;;

Never show a student a non exhaustive pattern matching :)

Pierre Weis

INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://pauillac.inria.fr/~weis/


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Re: [Caml-list] small exercise

[Pierre Weis]

> altavillasalvatore@libero.it wrote:
> > Hi all,
> > 
> > I do not succeed to develop the following exercise:
> > I have need of your aid.
> > 
> > 
> > 
> > input:  string    "1.15.120.13.43.35.340.190.0"
> > 
> > output: int array=  [| 1; 15; 120; 13; 43; 35; 340; 190; 0; |] 
> > 
> >   : string -> int array
> > 
> > 
> > Regards.
[...]
> Just a hint look at the documentation of the following functions:
> 
> module        | function
> ------------------------------
> str           | split
> list          | map
> pervasives    | int_of_string
> array         | of_list
> 
> The answer fits on one (long) line.
> -- 
> Christophe Raffalli

I guess, you forgot the most appropriate module for the exercicise: Scanf.

Indeed, scanning the given input string to obtain the expected vector
only using Scanf.scanf is interesting and not completely trivial.

An additional question could be: write a general polymorphic reader
that can input vectors with elements of any simple basic type (say
bool, int, string, char, float). Define a string reader via partial
application of the polymorphic reader.

Last but not least could be: generalize (if necessary) the polymorphic
reader to read vectors of any given type. Apply this function to read
matrices of floating point numbers. Discuss the use of Scanf in place
of a combination of modules Str, List, Pervasives, Array, ...

Mmm. A trivial exercicise could show up to be interesting afterwards :)

Pierre Weis

INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://pauillac.inria.fr/~weis/


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