non-recursive functions in Python

non-recursive.py

# Credits: https://medium.com/@ujjawalsinhacool16021998/easily-convert-recursive-solutions-to-non-recursive-alternatives-4fa6e1acf702

# Simple function, two branches which does not return a value
def simple2_noreturn(inputs):
  CALL, HANDLE = 0, 1
  call_stack = [(CALL, inputs)]
  while call_stack:
    action, data = call_stack.pop()
    if action == CALL:
      call_stack.append((HANDLE, some_data))
      call_stack.append((CALL, some_other_data))
      call_stack.append((CALL, some_data))
    else: # HANDLE
      # do something with data
 
# Simple function, 2 branches, which returns a value
def simple2_return(inputs):
  CALL, HANDLE = 0, 1
  call_stack = [(CALL, inputs)]
  return_stack = []
  while call_stack:
    action, data = call_stack.pop()
    if action == CALL:
      # place some condition here to prevent
      # endless looping, and to cut the tree
      # branches somewhere.
      call_stack.append((HANDLE, some_data))
      call_stack.append((CALL, some_other_data))
      call_stack.append((CALL, some_data))
    else: # HANDLE
      # pop items from return_stack
      # use them to calculate something
      # and push that something to return_stack
  return return_stack[-1] # return top value from the return_stack
 

# Simple function, 3 branches, third one conditional, which returns a value.
def simple2_return(inputs):
  CALL, HANDLE = 0, 1
  call_stack = [(CALL, inputs)]
  return_stack = []
  while call_stack:
    action, data = call_stack.pop()
    if action == CALL:
      # place some condition here to prevent
      # endless looping, and to cut the tree
      # branches somewhere.
      call_stack.append((HANDLE, some_data))
      call_stack.append((CALL, some_other_data))
      call_stack.append((CALL, some_data))
      if some condition passes:
        call_stack.append((CALL, some_other_data))
    else: # HANDLE
      # pop items from return_stack
      # use them to calculate something
      # and push that something to return_stack
  return return_stack[-1] # return top value from the return_stack
 
  
# Simple function, 3 branches, third one looping, which returns a value.
def simple2_return(inputs):
  CALL, HANDLE = 0, 1
  call_stack = [(CALL, inputs)]
  return_stack = []
  while call_stack:
    action, data = call_stack.pop()
    if action == CALL:
      # place some condition here to prevent
      # endless looping, and to cut the tree
      # branches somewhere.
      call_stack.append((HANDLE, some_data))
      call_stack.append((CALL, some_other_data))
      call_stack.append((CALL, some_data))
      # Preprocessing of while condition
      while some condition passes:
        call_stack.append((CALL, some_other_data))
        # Postprocessing of while condiion
    else: # HANDLE
      # pop items from return_stack
      # use them to calculate something
      # and push that something to return_stack
  return return_stack[-1] # return top value from the return_stack