"""
Authors: Peter Mawhorter
Consulted:
Date: 2021-11-7
Purpose: Solutions for lab 12 part 1 on fruitful recursion.
"""


def sumUpTo(n):
    """
    Returns the sum of all positive integers up to and including the
    specified number.
    """
    if n == 0:
        # Base case: return 0
        return 0
    else:
        # Recursive case: compute sum of smaller numbers; add n
        return n + sumUpTo(n - 1)


def addToEach(nums, add):
    """
    Returns a list where the 'add' number has been added to each number
    in the given list of numbers.
    """
    if len(nums) == 0:
        # Base case: empty list
        return []
    else:
        # Recursive case: split into first + rest
        first = nums[0]
        rest = nums[1:]

        # Add to first; recurse on rest
        return [ first + add ] + addToEach(rest, add)


def countLs(word):
    """
    Returns the number of times 'l' or 'L' appears in the given word.
    """
    if len(word) == 0:
        # Base case: no letters -> no 'l's
        return 0
    else:
        # Recursive case: Split into first and rest
        first = word[0]
        rest = word[1:]

        # Count the first letter or not
        if first in 'lL':
            count = 1
        else:
            count = 0

        # Add 1 (or 0) to count from rest
        return count + countLs(rest)