lec16.py

### REVIEW ###

# Mutation
def square_tree(t):
  t.label = t.label ** 2
  for b in t.branches:
    square_tree(b)
    
# New Tree

def square_tree(t):
  new_branches = [square_tree(b) for b in t.branches]
  return Tree(t.label ** 2, new_branches)
                   
 

### Let's put it all together ###

Link(1) 

Link(1, 2, 3) #should this work?

Link(1, 2) # should this work?

Link(1, Link(2)) #do i need to do this? 

### String Rep ### 

a = Link(1, Link(2, Link(3)))
a

print(a)

b = Link(Link(1), Link(2, Link (3)))
print(b)

### Mutation ###

a = Link(1, Link(2))
a.first = 100

a.rest.rest = a 

### Linked List Range ###

def range_link(start, end):
  if start >= end:
    return Link.empty
  return Link(start, range_link(start + 1, end))
              
def range_link_iter(start, end):
   s = Link(start)
   curr = s
   start += 1
   while start < end:
       s.rest = Link(start)
       s = s.rest
       start += 1
   return curr
              
              
 ### Map Linked List ###
              
def map_link(f, s):
    if s is Link.empty:
            return Link.empty
     return Link(f(s.first), map_link(f, s.rest))
              
 def map_link(f, s):
    while s is not Link.empty:
              lnk.first = f(lnk.first)
              lnk = lnk.rest
              
### Filter Link ###
              
def filter(f, s):
       if s is Link.empty:
              return Link.empty
       elif f(s.first):
            return Link(s.first, filter_link(f, s.rest))
       return filter_link(f, s.rest)