#include<stdio.h>

typedef struct listcell * cell;
struct listcell
{
  int head;
  cell tail;
};


cell cons(int h, cell t)
{
  cell newcell;
  newcell = (cell) malloc(sizeof(struct listcell));
  newcell->head = h;
  newcell->tail = t;
  return newcell;
}

void printlist(cell L)
{
  if (L == NULL) printf("\n");  
    else {  printf("%d ",L->head);
          printlist(L->tail);
          }
}// printlist

int listlength(cell L)
{
  if (L == NULL) return 0;
    else return 1 + listlength(L->tail);
}

cell delete1(int x,cell L) // deletes first x from L: nonstructive
{  if (L == NULL) return L;
    else if (x == L->head) return L->tail;
       else return cons(L->head,delete1(x,L->tail));
}

cell append(cell A, cell B)
{
  if (A == NULL) return B;
    else return cons(A->head,append(A->tail,B));
}

int doubleit(int x) { return x+x; }
int squareit(int x) { return x*x;}

cell map( int (*f)(int), cell L )
{ if (L == NULL) return L;
		   else cons((*f)(L->head),map(f,L->tail));
}


int main()
{
  cell A, B;

  A = cons(1,cons(3,cons(5,NULL)));
  B = cons(2,cons(4,cons(6,cons(8,NULL))));
  printlist(A);
  printlist(B);

  printlist(map(doubleit,A));
  printlist(map(squareit,A));
  /*
  B = delete1(6,B);
  printlist(B);
  printf("length of B is %d\n",listlength(B));
  */
  return 0;
}