Script started on Wed Oct 16 12:29:15 2024
mweeks@air:C_ch11$ echo 9841
9841
mweeks@air:C_ch11$ cat types_of_pointers.c 


    int *p;    /* points only to integers */
    char *str; /* points only to characters */
    double *q; /* points only to doubles */
    int i, j, a[10], *p, *q ; /* p and q point to integers */


    int i=2, j, *p; /* p points nowhere */
    p = &i; /* p points to integer variable i */
    j = *p; /* same as j=i */


    int i=2, *p=&i; /* p points to variable i */


    int i, j, *p = &i;
    i = 1;
    printf("i = %d\n", i);
    printf("*p = %d\n", *p);

    *p = 4;

    printf("i = %d\n", i);
    printf("*p = %d\n", *p);

    j = *&i;
    printf("j = %d\n", j);

mweeks@air:C_ch11$ cat const_ex1.c 

        void f(const int *p)
        {
            *p = 0; /*  wrong: p is a pointer
                        to a ``constant integer'' */
        }

mweeks@air:C_ch11$ cat bad_ptr.c 
Don't return a ptr to local var

        int *f(void)
        {
            int a;
            ...
            return &a;
        }

Once 'f' returns, the variable 'a' does not exist, so the pointer to it
will be invalid.

mweeks@air:C_ch11$ ls bad*c
bad_avg_sum.c	bad_ptr.c
mweeks@air:C_ch11$ cat bad_avg_sum.c 
    void avg_sum (float a[], int n, float *avg, float *sum)
    {
        int i;
        sum = 0.0;           //  *sum = 0.0
        for (i=0;i<n;i++)
            sum += a[i];     //  *sum = *sum + a[i]
        avg = sum / n;       //  *avg= *sum / n
    }

// This has problems
mweeks@air:C_ch11$ cd ../C_ch12
mweeks@air:C_ch12$ cat ch12_4.c 
#include <stdio.h>

int main(){
    int a[10]; 
            *a = 7;          // modify a[0] 
            *(a + 2) = 13;   // modify a[2] 
            
            while ( *a != 0 ){ 
                //a++; // wrong
                
                a = a + 1; // this is not correct either
                
                }
}
mweeks@air:C_ch12$ echo "you can combine * with ++"
you can combine * with ++
mweeks@air:C_ch12$ echo "*(p++)"
*(p++)
mweeks@air:C_ch12$ echo "compare pointers   (p <= q) "
compare pointers   (p <= q) 
mweeks@air:C_ch12$ ls
ch12_1.c		ch12_4.c		char_ptr_to_int.c
ch12_2.c		ch12_5.c		find_largest.c
ch12_3.c		ch12_5b.c
ch12_3_messed_up.c	ch12_6.c
mweeks@air:C_ch12$ cat char_ptr_to_int.c 
#include <stdio.h>

#define M 10
        
int main() {

  // Question posed by Avyuktkrishna, Fall 2023
  int i, a[M] = {1, 2, 3, 4, 5, 6};
  char *A;
  A = &a[0];  // These are incompatible types
  int sum = 0;
  for (i=0; i<M; i++) {
    printf("sum = sum + %d\n", *A);
    sum = sum + *A;    
  }
  printf("%d\n", sum);
    
  return 0;
}
mweeks@air:C_ch12$ cat find_largest.c


// Either of these works
int find_largest(int a[], int n) {
   // ...
}

int find_largest(int *a, int n) {
   // ...
}

mweeks@air:C_ch12$ cat ch12_5.c 
#include <stdio.h>

#define NUM_ROWS 5
#define NUM_COLS 5

int main(){
// Example: Initialize a 2D array
// *Traditional method*

        int a[NUM_ROWS][NUM_COLS]; 
        int row, col; 
        for (row = 0; row < NUM_ROWS; row++) 
            for (col = 0; col < NUM_COLS; col++) 
                a[row][col] = 0; 

// *Using a pointer*

        int *p; 
        for (p = &a[0][0]; p < &a[NUM_ROWS-1][NUM_COLS]; p++) 
            *p = 0; 
        return 0;
}
mweeks@air:C_ch12$ cd ~/Desktop/Projects/fox_and_geese/
mweeks@air:fox_and_geese$ make
gcc -c NN.c
cc    -c -o fox_and_geese.o fox_and_geese.c
gcc fox_and_geese.c -o fox_and_geese NN.o fileIO.o mystrings.o RNG.o
mweeks@air:fox_and_geese$ exit
exit

Script done on Wed Oct 16 13:45:26 2024