This lab provides additional exercises on iteration over lists.

Download lab6.zip, place it in your `cpe101`

directory, and unzip the file.

Develop these functions in the `fold`

directory in files
`fold.py`

and `fold_tests.py`

.

Each of the functions for this part of the lab is to be implemented using the fold pattern. In this pattern, the values in the input list are combined in some manner (e.g., an arithmetic or relational operation) to compute a single result value. Each of these functions will use a local variable (or local variables) to hold the computed value as the list is traversed. This variable is often updated at each step of the iteration.

The `sum`

function returns the sum of all values in the
input list.

The `index_of_smallest`

function returns the index of the
smallest value in the input list. If the list is empty (i.e., the
length is ≤ 0), then the function returns -1.

The `nearest_origin`

function returns the index of the
point nearest the origin. If the list is empty, then the function
returns -1.

For this part of the lab you will develop a function that will be of
use in the last assignment of the quarter. In `groups.py`

,
define the following function.

The `groups_of_3`

function takes a list of values as its only
argument. This function will group the elements of the input list into
groups of three (i.e., the first three consecutive values form a group,
the second three form a group, etc.). This function must return a list
of lists where each sublist (excluding, perhaps, the last) is a group of
three values. If there are not enough values to fill the last grouping,
then it will contain fewer than three values.

As examples, consider the following.

>>> groups_of_3([1,2,3,4,5,6,7,8,9])

[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

>>> groups_of_3([1,2,3,4,5,6,7,8])

[[1, 2, 3], [4, 5, 6], [7, 8]]

The `while`

statement is another way to specify iteration,
though it is typically used for a different type of iteration than that over
lists.

For this part of the lab, edit the `loops.py`

file in the
`loops`

directory. Complete the `while_version`

function by translating the `for`

statement from the
`for_version`

function into an equivalent `while`

statement. Think carefully about the different steps in the `for`

statement.

Demonstrate the test cases from each part of the lab to your instructor to have this lab recorded as completed. In addition, be prepared to show the source code to your instructor.

The handin command will vary by section.

Those in Aaron Keen's sections will not submit the lab.