How can I translate this program from Vala to Genie?

Question

I guess there are references out there with a few examples, but my Google-fu failed me and so did the documentation page for Genie.

Let's take a very specific example, some Vala code from there:

using GLib;
using Gsl;

public class Test : GLib.Object
{
        public static void main (string[] args)
        {
                double[] a_data = new double[] { 0.18, 0.60, 0.57, 0.96,
                                                 0.41, 0.24, 0.99, 0.58,
                                                 0.14, 0.30, 0.97, 0.66,
                                                 0.51, 0.13, 0.19, 0.85 };

                double[] b_data = new double[] { 1.0, 2.0, 3.0, 4.0 };

                MatrixView m = MatrixView.array (a_data, 4, 4);
                VectorView b = VectorView.array (b_data);

                Vector x = new Vector (4);

                int s;

                Permutation p = new Permutation (4);

                LinAlg.LU_decomp ((Matrix)(&m.matrix), p, out s);
                LinAlg.LU_solve ((Matrix)(&m.matrix), p, (Vector)(&b.vector), x);

                stdout.printf("x = \n");
                Vector.fprintf(stdout, x, "%g");
        }
}

Here is how I tried to convert that program into Genie:

[indent=4]

uses Gsl

init
    a_data: array of double = { 0.18, 0.60, 0.57, 0.96,
                                0.41, 0.24, 0.99, 0.58,
                                0.14, 0.30, 0.97, 0.66,
                                0.51, 0.13, 0.19, 0.85 }
    b_data: array of double = { 1.0,  2.0,  3.0,  4.0 }

    var m = Gsl.MatrixView.array(a_data, 4, 4)
    var b = Gsl.VectorView.array(b_data)

    var x = new Gsl.Vector(4)

    s:int = 0

    var p = new Gsl.Permutation(4)

    Gsl.LinAlg.LU_decomp(m, p, out s)
    Gsl.LinAlg.LU_solve(m, p, b, x)

    print "x =\n%g", x

which should be correct as per this reference.

But it fails:

LA.gs:12.28-12.32: error: syntax error, expected identifier
    var m = Gsl.MatrixView.array(a_data, 4, 4)
                           ^^^^^
LA.gs:13.28-13.32: error: syntax error, expected identifier
    var b = Gsl.VectorView.array(b_data)
                           ^^^^^
Compilation failed: 2 error(s), 0 warning(s)

So, could anyone please explain to me what that particular error means? What is an identifier in the context of Genie?

And what is the correct way to call such a static method in Genie?

Answer 1

array is a reserved keyword, so you have to add an @-sign in front of the reserved keyword:

var m = Gsl.MatrixView.@array(a_data, 4, 4)
var b = Gsl.VectorView.@array(b_data)

The print line is also incorrect, I have fixed most problems:

[indent=4]

uses Gsl

init
    a_data: array of double = { 0.18, 0.60, 0.57, 0.96,
                                0.41, 0.24, 0.99, 0.58,
                                0.14, 0.30, 0.97, 0.66,
                                0.51, 0.13, 0.19, 0.85 }
    b_data: array of double = { 1.0,  2.0,  3.0,  4.0 }

    var m = Gsl.MatrixView.@array(a_data, 4, 4)
    var b = Gsl.VectorView.@array(b_data)

    var x = new Gsl.Vector(4)

    s:int = 0

    var p = new Gsl.Permutation(4)

    Gsl.LinAlg.LU_decomp((Matrix) m, p, out s)
    Gsl.LinAlg.LU_solve((Matrix) m, p, (Vector) b.vector, x)

    stdout.printf("x =\n")
    Vector.fprintf(stdout, x, "%g")

This still doesn't compile, because the LU_ methods need a typecast that I'm not 100% sure how to do.

Update: This code compiles and runs, but I have no idea if its actually correct:

[indent=4]

uses Gsl

init
    a_data: array of double = { 0.18, 0.60, 0.57, 0.96,
                                0.41, 0.24, 0.99, 0.58,
                                0.14, 0.30, 0.97, 0.66,
                                0.51, 0.13, 0.19, 0.85 }
    b_data: array of double = { 1.0,  2.0,  3.0,  4.0 }

    var m = Gsl.MatrixView.@array(a_data, 4, 4)
    var b = Gsl.VectorView.@array(b_data)

    var x = new Gsl.Vector(4)

    s:int = 0

    var p = new Gsl.Permutation(4)

    mp : MatrixView* = &m
    vp : Vector** = &(b.vector)

    Gsl.LinAlg.LU_decomp((Matrix) mp, p, out s)
    Gsl.LinAlg.LU_solve((Matrix) mp, p, (Vector) vp, x)

    stdout.printf("x =\n")
    Vector.fprintf(stdout, x, "%g")