.. _exercise_lambda_magic:

************************
lambda and keyword Magic
************************

Goals
=====


    * A bit of lambda
    * functions as objects
    * keyword evaluation


Task
----

Write a function that returns a list of n functions,
such that each one, when called, will return the input value,
incremented by an increasing number.

Use a for loop, ``lambda``, and a keyword argument

**Extra credit:**

Do it with a list comprehension, instead of a for loop

Not clear? here's what you should get...

Example calling code
---------------------

.. code-block:: ipython

    In [96]: the_list = function_builder(4)
    ### so the_list should contain n functions (callables)
    In [97]: the_list[0](2)
    Out[97]: 2
    ## the zeroth element of the list is a function that add 0
    ## to the input, hence called with 2, returns 2
    In [98]: the_list[1](2)
    Out[98]: 3
    ## the 1st element of the list is a function that adds 1
    ## to the input value, thus called with 2, returns 3
    In [100]: for f in the_list:
        print(f(5))
       .....:
    5
    6
    7
    8
    ### If you loop through them all, and call them, each one adds one more
    to the input, 5... i.e. the nth function in the list adds n to the input.


See the test code in :download:`test_lambda.py <../solutions/extras/lambda/test_lambda.py>`