[Caml-list] laconical input from a file for arrays and/or matrices

[Caml-list] laconical input from a file for arrays and/or matrices

[Khamenia, Valery]

Hi OCaMLers,

  here goes my usual way to input ASCII matrices from file in C++:

//  -------  start of fragment -----------
#include <iostream>
#include <vector>
using namespace std;

void input_matrix(vector<vector<double > >&vec) {
  int m, n;
  cin >> m;
  cin >> n;
  vec.resize (m);
  for( int i = 0; i<m; i++)
    vec[i].resize(n);
  for( int i = 0; i<m; i++)
    for( int j = 0; j<n; j++) 
      cin >> vec[i][j]; 
}
//  -------- end of fragment -------------

then for matrix :

  3
  3
  1 2 3 
  4 5 6
  7 8 9

stored in ASCII text file mymatrix.dat

i just run my program:

 % myprogram < mymatrix.dat

and it is done.

Thus, the few lines of code and i can apply all math I need. 

Is there any similar ascetic way in OCaML for 
doing the same?

Thanks a priori,
kind regards,
Valery A.Khamenya
---------------------------------------------------------------------------
Bioinformatics Department
BioVisioN AG, Hannover

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Re: [Caml-list] laconical input from a file for arrays and/or matrices

[samsaga2]

let output_matirx m = output_value stdout m
let input_matrix () = input_value stdin

But no compatible with c++ files :-P

Khamenia, Valery wrote:

>Hi OCaMLers,
>
>  here goes my usual way to input ASCII matrices from file in C++:
>
>//  -------  start of fragment -----------
>#include <iostream>
>#include <vector>
>using namespace std;
>
>void input_matrix(vector<vector<double > >&vec) {
>  int m, n;
>  cin >> m;
>  cin >> n;
>  vec.resize (m);
>  for( int i = 0; i<m; i++)
>    vec[i].resize(n);
>  for( int i = 0; i<m; i++)
>    for( int j = 0; j<n; j++) 
>      cin >> vec[i][j]; 
>}
>//  -------- end of fragment -------------
>
>then for matrix :
>
>  3
>  3
>  1 2 3 
>  4 5 6
>  7 8 9
>
>stored in ASCII text file mymatrix.dat
>
>i just run my program:
>
> % myprogram < mymatrix.dat
>
>and it is done.
>
>Thus, the few lines of code and i can apply all math I need. 
>
>Is there any similar ascetic way in OCaML for 
>doing the same?
>
>Thanks a priori,
>kind regards,
>Valery A.Khamenya
>

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Re: [Caml-list] laconical input from a file for arrays and/or matrices

[Virgile Prevosto]

:

Le lundi 02 février, à 11h57 +0100,
samsaga2 a écrit:

> let output_matirx m = output_value stdout m
> let input_matrix () = input_value stdin
> 
> But no compatible with c++ files :-P
> 
> Khamenia, Valery wrote:
> >  here goes my usual way to input ASCII matrices from file in C++:

# let x = Array.make_matrix 1 1 3 in output_value stdout x;;
¦¾C
- : unit = ()

I doubt that we can speak of ASCII matrices in that case ;-)

Anyway, it's not so difficult to obtain a code fragment close to the
C++ one, thanks to the Array and Scanf modules: 

(* CAML version. *)
let input_matrix () = 
  let m = read_int () in
  let n = read_int () in
  let matrix = Array.make_matrix m n 0. in
    for i = 0 to (m - 1)  do
      for j = 0 to (n -1) do
          matrix.(i).(j) <-  Scanf.scanf "%f " (fun x -> x)
      done
    done;
    matrix;;
val input_matrix : unit -> float array array = <fun>

Of course, you'll have to adapt the formatting instruction of scanf to
your datas (the main problem here is that scanf expects to fins a blank
after each entry, which means that your file must end with a newline or
a space).

-- 
E tutto per oggi, a la prossima volta
Virgile

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Re: [Caml-list] laconical input from a file for arrays and/or matrices

[Richard Jones]

Probably not quite what you want, but I have a library for reading and
writing comma-separated values (CSV) files here:

http://www.merjis.com/developers/csv/
http://www.merjis.com/developers/csv/ocaml-csv-1.0.1.tar.gz

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://www.j-london.com/
Merjis Ltd. http://www.merjis.com/ - improving website return on investment
'There is a joke about American engineers and French engineers. The
American team brings a prototype to the French team. The French team's
response is: "Well, it works fine in practice; but how will it hold up
in theory?"'

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Re: [Caml-list] laconical input from a file for arrays and/or matrices

[Issac Trotts]

On Mon, Feb 02, 2004 at 11:42:18AM +0100, Khamenia, Valery wrote:
> Hi OCaMLers,
> 
>   here goes my usual way to input ASCII matrices from file in C++:
> 
> //  -------  start of fragment -----------
> #include <iostream>
> #include <vector>
> using namespace std;
> 
> void input_matrix(vector<vector<double > >&vec) {
>   int m, n;
>   cin >> m;
>   cin >> n;
>   vec.resize (m);
>   for( int i = 0; i<m; i++)
>     vec[i].resize(n);
>   for( int i = 0; i<m; i++)
>     for( int j = 0; j<n; j++) 
>       cin >> vec[i][j]; 
> }
> //  -------- end of fragment -------------
> 
> then for matrix :
> 
>   3
>   3
>   1 2 3 
>   4 5 6
>   7 8 9
> 
> stored in ASCII text file mymatrix.dat
> 
> i just run my program:
> 
>  % myprogram < mymatrix.dat
> 
> and it is done.
> 
> Thus, the few lines of code and i can apply all math I need. 

Here's a way to do it with camlp4.  You get OCaml-style comments 
for free from Genlex this way:

#load "camlp4o.cma";; 
open Genlex;;

let input_matrix channel = 
  let read_number = parser
      [< 'Int i >] -> float i
    | [< 'Float f >] -> f in
  let rec read_nums n = 
    if n = 0 
      then parser [< >] -> [] 
      else parser [< head=read_number; tail=read_nums (n-1) >] -> head::tail in 
  let rec read_matrix_data m n = 
    if m = 0 
      then parser [< >] -> []
      else parser
        [< row = read_nums n; rest = read_matrix_data (m-1) n >] -> 
          (Array.of_list row) :: rest in
  let read_matrix = parser 
    [< 'Int m; 'Int n; rest >] ->
      let rows = read_matrix_data m n rest in
      Array.of_list rows in
  let charstream = Stream.of_channel channel in
  let lexer = Genlex.make_lexer [] charstream in
  read_matrix lexer;;

input_matrix stdin;;

-- 
Issac Trotts
http://redwood.ucdavis.edu/~issac

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