/*
 * Playing around with matrices in C.
 *
 * Remember that with the include <math.h>, this needs to find 
 * the math library libm, and so needs to be compiled with the "-lm" flag.
 * On cs.marlboro.edu, compile and run it with
 *
 *    $ cc -march=pentium4 -O3 -lm matrix.c -o matrix
 *    $ ./matrix
 *
 *
 *    x[n]  means *(x+n)  which is "de-reference pointer at location x + n
 *    &x[0] means same as x
#     
 *
 * Feb 24 2005, Jim M in class
 */

#include <stdio.h>
#include <math.h>

#define NSIZE 10;

void print_matrix(int*, int);
void print_matrix2D( int m[NSIZE][NSIZE] );

int main(){
  int MAX = 100;

  int x[MAX];          /* allocate space for x[0], x[1], ..., x[99] integers */
  int N = sqrt(MAX);   /* size of 2 dimensional grid */

  int y[NSIZE][NSIZE];       /* a two dimensional matrix ! */

  int row = 3;  /* row, column index of matrix */
  int col = 1;

  int i,j;        /* loop counter */

  for ( i = 0; i < MAX; i++ ){
    x[i] = 0;
  }

  for ( i = 0; i < 10; i++ ){
    for ( j = 0; j < 10; j++ ){
      y[i][j] = 0;
    }
  }

  x[0] = 42;    /* a number we can remember */
  x[1] = 50;
  x[2] = 51;
  x[3] = 101;   /* some other random number */
  x[4] = 103;

  y[1][3] = 42;
  printf(" y[1][3] = '%i' \n", y[1][3]);
  print_matrix2D(y);
  /* NO: printf(" y[13]   = '%i' \n", y[13]);  */
  /* NO: printf(" *(y+13) = '%i' \n", *(y+13)); */
  /* NO: print_matrix(y, 100);  */

  printf(" size of int is %i \n", sizeof(int));
  printf(" \n");

  printf(" x is %p\n", x);
  printf(" x[0] is %i\n", x[0]);
  printf(" *x is %i \n", *x);
  printf("\n");

  printf(" &x[1] is %p \n", &x[1]);
  printf(" x[1] is %i \n", x[1]);
  printf(" *(x+1) is %i \n", *(x+1) );

  //printf(" x[3] = %i \n",   *(x+3*sizeof(int))   );

  // printf(" Here's the matrix after we set it to zero : \n");
  // print_matrix(x, MAX);

  x[row*N + col] = 6;
  // printf(" Here's the matrix after we set 3,1 to 6 : \n");
  // print_matrix(x, MAX);

  return 0;

}

//
// prints a matrix which has been declared as a two dimensional thingy.
//
void print_matrix2D( int m[NSIZE][NSIZE]){
  int row, col;
  for (row = 0; row < NSIZE; row++){
    for (col = 0; col < NSIZE; col++){
      printf(" %i ", m[row][col]);
    }
    printf("\n");
  }
}

//
// prints a matrix which was declared as a one dimensional thingy.
//
void print_matrix( int m[], int size){
  int N = sqrt(size);
  int row, col;
  for (row = 0; row<N; row++){
    for (col = 0; col<N; col++){
      printf(" %i ", m[ row*N + col ]);
    }
    printf("\n");
  }
}