SE250:lab-4:hals016

Lab 4

I started coding the length method by writing a for loop similiar to the one in the print_list method. The difference is that there needed to be a counter to keep track of all the elements.

int length(Cons* list) {
  int i;
  if (list->tail == 0)
    return 0;
  else {
    for (i = 0; list != nil; list = list->tail ) {
      i++;
    }
    return i;
  }
}

When writing code to check the first element in the cons cell, I first made a condition that if the 'list->==nil' then 0 would be returned. Else 'list->head' would be returned.

element_t first(Cons* list) {
  if (list->tail == nil)
    return 0;
  else
    return list->head;
}

Doing the second element was harder because it required a loop, I used the same loop and conditions for the third and fourth element but with the condition incremented slightly for each method.

element_t second(Cons* list) {
  int i;
  if (list->tail == nil)
    return 0;
  for (i = 0; i<1; list = list->tail ) {
    i++;
  }
  if (!(list->head==0))
    return list->head;
  else
    return 0;
}

The code for the nth element was straightforward because a template of element at second can be used with the for loop using the variable that indicats which element wants to be viewed.

element_t nth(int n,Cons* list) {
  int i;
  if (list->tail == nil && n>0 )
    return 0;
  else {
    for (i = 0; i<(n-1); list = list->tail ) {
      i++;
    }
  }
  if (!(list->head==0))
    return list->head;
  else
    return 0;
}