//////////////////////////////////////////////////////////////////
//Dynamically Allocated Matrix struct
//
//Demo program which showcases a clean way to work with matrices.
//
//Matthew Miller
//July 2007
/////////////////////////////////////////////////////////////////

#include <stdlib.h>
#include <stdio.h>

/////////////////////////////////////////////////////////////
//Matrix struct
//
//Used to store a matrix and it's dimensions. //Allows for clean syntax when using matrices.
//
//To declare a new matrix: Matrix A;
/////////////////////////////////////////////////////////////
typedef struct
{
double ** M;
int m;
int n;
}Matrix;

//////////////////////////////////////////////////////////
//Allocate the data portion of a Matrix, given dimensions.
//
//Note that this does not allocate the struct itself, //only the data protion (double ** M).
//
//Arguments
//
//Matric * mat : Pointer to a Matrix. //int m,n      : Number of rows/columns.
///////////////////////////////////////////////////////////
void MatrixAlloc(Matrix * mat,int m,int n)
{
int i;

//store dimensions in matrix
mat->m=m;
mat->n=n;
//note the arrow operator (->) is used becuase //mat is a pointer to a struct 
//allocate m row arrays -- this gives us the first subscript
mat->M=(double **) malloc(m*sizeof(double*));

//allocate n elements for each row -- this gives us the second subscript for(i=0;i<m;i++)
 {
  mat->M[i]=(double *) malloc(n*sizeof(double));
 }

//entries in mat->M can now be referenced as mat->M[i][j] }

//Self explanitory
void printMatrix(Matrix * mat)
{
int i,j;

for(i=0;i<mat->m;i++)
 {
  for(j=0;j<mat->n;j++)
   {
    printf("%g ",mat->M[i][j]);
   }
 printf("\n");
}
}

//Just a test function
void foo(Matrix * mat)
{
int i,j;

printf("Foo!\n");

for(i=0;i<mat->m;i++)
 {
  for(j=0;j<mat->n;j++)
   {
    mat->M[i][j]=(i+j)%(mat->m);
   }
 } }

int main()
{
//a 10x5 matrix sounds good
int m = 10;
int n = 5;

//declare this way to get struct allocation for free
Matrix mat;

//allocate the data portion of the matix, note the reference operator (&)
MatrixAlloc(&mat,m,n);

//foo it
foo(&mat);

//print it
printMatrix(&mat);

return 0;
}