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scilab: fix doc on matrices (and arrays)

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Simon Marchetto 2014-03-12 17:30:07 +01:00
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Doc/Manual/Scilab.html
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@ -625,10 +625,11 @@ ans =
<p>
One-dimensional arrays are supported whether as global variables or functions arguments.
Arrays are mapped in SWIG as pointers. But primitive type arrays are automatically converted from/to Scilab matrices.
</p>
<p>
Global arrays are wrapped through accessor functions.
Global arrays are manipulated in Scilab through accessor functions.
For example with two global arrays x and y:
</p>
@ -650,7 +651,7 @@ void initArrays()
%}
</pre></div>
<p>Two Scilab functions are generated for each array: a getter _get() and a setter _set(), prefixed by the array name.
<p>Two Scilab functions are generated for each array: a getter <tt>_get()</tt> and a setter <tt>_set()</tt>, prefixed by the array name.
Following is an example of use of these functions:
</p>
@ -682,113 +683,76 @@ And this C int array is automatically converted in output to a Scilab double vec
<H3><a name="Scilab_wrapping_matrices"></a>37.3.12 Matrices</H3>
<p>
Scilab uses matrices a lot for numerical mathematics and scientific visualization. Supporting matrices makes Scilab more convenient. For example:
Matrices can be implemented in several ways in C, here we focus on matrices implemented with pointer-to-pointer (ex: <tt>double**</tt>).
</p>
<div class="code"><pre>%module example
<p>
These matrices are mapped by default in SWIG as pointers.
There is no automatic conversion with Scilab matrices, for this, the <tt>matrix.i</tt> library has to be used.
</p>
<p>
Following is an example with functions working with matrices:
</p>
<div class="code"><pre>
%module example
%inline %{
double **new_matrix() {
int i;
// Returns the matrix [1 2; 3 4];
double **create_matrix() {
double **M;
M = (double **) malloc(4 * sizeof(double *));
M[0] = (double *) malloc(16 * sizeof(double));
for (i = 0; i &lt; 4; i++) {
M[i] = M[0] + 4 * i;
int i;
M = (double **) malloc(2 * sizeof(double *));
for (i = 0; i &lt; 2; i++) {
M[i] = (double *) malloc(2 * sizeof(double));
M[i][0] = 2 * i + 1;
M[i][1] = 2 * i + 2;
}
return M;
}
void set_m(double **M, int i, int j, double val) {
M[i][j] = val;
}
double get_m(double **M, int i, int j) {
// Gets the item M(i,j) value
double get_matrix(double **M, int i, int j) {
return M[i][j];
}
void print_matrix(double **M) {
// Sets the item M(i,j) value to be val
void set_matrix(double **M, int i, int j, double val) {
M[i][j] = val;
}
int i,j;
for (i = 0; i &lt; 4; i++) {
for (j = 0; j &lt; 4; j++) {
printf("%10g ", M[i][j]);
// Prints a matrix (2,2) to console
void print_matrix(double **M, int nbRows, int nbCols) {
int i, j;
for (i = 0; i &lt; 2; i++) {
for (j = 0; j &lt; 2; j++) {
printf("%3g ", M[i][j]);
}
printf("\n");
}
}
void mat_mult(double **m1, double **m2, double **m3) {
int i,j,k;
double temp[4][4];
for (i = 0; i &lt; 4; i++)
for (j = 0; j &lt; 4; j++) {
temp[i][j] = 0;
for (k = 0; k &lt; 4; k++)
temp[i][j] += m1[i][k] * m2[k][j];
}
for (i = 0; i &lt; 4; i++)
for (j = 0; j &lt; 4; j++)
m3[i][j] = temp[i][j];
}
%}
</pre></div>
<p> When wrapped, it would generate the following function:
</p>
<p>_wrap_new_matrix(): generate a new matrix.
</p>
<p>_wrap_set_m(M, i, j, a): set M(i, j) to be value a.
</p>
<p>_wrap_get_m(M, i, j): get the value of M(i, j).
</p>
<p>_wrap_print_matrix(M): print the matrix M.
</p>
<p>_wrap_mat_mult(A, B, C): compute the A * B and the result is stored into C.
</p>
<p>It can be used like this:
<p>
These functions are used like this in Scilab:
</p>
<div class="targetlang"><pre>
--&gt; exec loader.sce
--&gt; m = create_matrix();
--&gt; x = new_matrix();
--&gt; for i = 0 : 3;
--&gt; for j = 0 : 3;
--&gt; set_m(x, i, j, i + j);
--&gt; end;
--&gt; end;
--&gt; print_matrix(m);
1. 2.
3. 4.
--&gt; print_matrix(y);
0 1 2 3
1 2 3 4
2 3 4 5
3 4 5 6
--&gt; y = new_matrix();
--&gt; for i = 0 : 3;
--&gt; for j = 0 : 3;
--&gt; set_m(y, i, j, i - j);
--&gt; end;
--&gt; end;
--&gt; set_matrix(m, 1, 1, 5.);
--&gt; print_matrix(y);
0 -1 -2 -3
1 0 -1 -2
2 1 0 -1
3 2 1 0
--&gt; z = new_matrix();
--&gt; mat_mult(x, y, z);
--&gt; print_matrix(z);
14 8 2 -4
20 10 0 -10
26 12 -2 -16
32 14 -4 -22
--&gt; get_matrix(m, 1, 1)
ans =
5.
</pre></div>