/* Cons.c, <a href = "Cons.c">~comp210/Labs/lab14/Cons.c</a>.
 * 96.Dec.02, Ian Barland
 * A sample program for implementing lists in C.
 */

#include <stdlib.h>     // for NULL
#include <iostream.h>


// Define the structure
struct Cons {
  int   car;
  Cons* cdr;
  };


/* makeCons
 * create a list with desired car and cdr
 */
Cons* makeCons( int datum, Cons* rest ) {
  Cons* result;          // This is the value we'll return.
  result = new Cons;     // Create the new structure (with garbage contents).

  result->car = datum;   // Set up the innards of the structure.
  result->cdr = rest;

  return result;
  }

/* printWoParens
 * Print the elements of a list seperated by a space (only).
 * Intended as a helper to print().
 */
void printWoParens( Cons* l ) {
  if (l == NULL)
    return;
  else {
    cout << " " << l->car;
    printWoParens( l->cdr );
    }
  }

/* print
 * print a list with surrounding parentheses.
 */
void print( Cons* l ) {
  cout << "(";
  printWoParens( l );
  cout << ")";
  }


/* numsDown( n )
 * Return a list with integers n..1, in that order.
 */
Cons* numsDown( int n ) {
  if (n == 0)
    return NULL;
  else
    return makeCons( n, numsDown( n-1 ));
  }


/* length
 * Given a list, return its length.
 */
int length( Cons* l ) {
  //---  you complete this function! ---
  return -99;
  }


/* main
 * Just run some test cases.
 */
int main() {
  Cons* l1;
  Cons* l2;
  Cons* l3;

  l1 = NULL;
  l2 = makeCons( 3, makeCons( 5, makeCons( 4, NULL )));
  l3 = numsDown( 10 );
  l3 = makeCons( 17, l3->cdr );

  cout << "l1 is: ";
  print( l1 );
  cout << ", with length " << length( l1 ) << "." << endl;

  cout << "l2 is: ";
  print( l2 );
  cout << ", with length " << length( l2 ) << "." << endl;

  cout << "l3 is: ";
  print( l3 );
  cout << ", with length " << length( l3 ) << "." << endl;

  return 0;
  }