This 3-part homework provides some basic practice in Ruby as well as accustomizing you to testing as a regular part of your workflow.
The code provided here follows a fairly standard Ruby convention: program
files are stored in lib/ and the test files are stored in spec/.
(We are usng the RSpec unit-testing framework; if we were using Ruby's default
framework, known as Test::Unit, the test files would be under
test/.)
IMPORTANT NOTE: Before starting this assignment you will need to install the ruby rspec gem in you cloud9 environment. You can to this by entering the following command on the terminal:
gem install rspec
The starter code for the assignment is in lib/ruby_intro.rb. When you are done, you can
submit this single file to the ICON HW1 dropbox as follows:
- in the Workspace menu along the left side of your Cloud9 window, right click on the lib/ruby_intro.rb file and select "Download". This will download the file from Cloud9 to the "Downloads" folder on your local computer.
- Submit the downloaded file to the ICON HW1 dropbox.
The filesspec/part[123]_spec.rb contain RSpec tests for each of the three
parts. For example, to test your answers to Part 1, use the command:
rspec spec/part1_spec.rb
The command rspec with no arguments runs all of the tests in
the files spec/*_spec.rb.
-
The line numbers in the RSpec error report will give you guidance as to which tests failed. (You can check the RSpec documentation(http://rspec.info) to see how the
.rspecfile can be used to customize the output format.) -
If you want to be really cool, run
autotest. This will run all the tests inspec/, but every time you edit and save your code file, the tests are automatically re-run, so you don't have to run them manually. As we'll see later, this is the first step to TDD or test-driven development: write the tests before you write the code, watch the test fail, fill in the code and save the code file, then watch the test pass! Before runningautotest, you must first download some gems as follows:
gem install rspec-autotest
gem install autotest-standalone
Note: You will need to run autotest in a separate terminal window. To
terminate autotest, enter CTRL-C twice in rapid succession.
Here are the specifications for the functions you will need to implement for this assignment:
Check the Ruby 2.3.0 documentation on Array,
Hash and Enumerable as they could help tremendously with these
exercises. :-)
a. Implement a method sum(array) that takes an array of integers as
an argument and returns the sum of its elements. For an empty array it should return zero.
b. Implement a method max_2_sum(array) which takes an array of integers as an argument and
returns the sum of its two largest elements. For an empty array it should return zero. For
an array with just one element, it should return that element.
c. Implement a method sum_to_n?(array) that takes an array of integers and an additional
integer, n, as arguments and returns true if any two elements in the array of integers sum
to n. An empty array should sum to zero by definition.
You can check your progress by running:
rspec spec/part1_spec.rb
or by running autotest and leaving it running.
Check the documentation on String and Regexp as they could help tremendously with these exercises. :-)
a. Implement a method hello(name) that takes a string representing a name and returns the
string "Hello, " concatenated with the name.
b. Implement a method starts_with_consonant?(s) that takes a string and returns true if it starts
with a consonant and false otherwise. (For our purposes, a consonant is any letter other than
(A, E, I, O, U.) NOTE: be sure it works for both upper and lower case and for nonletters!
c. Implement a method binary_multiple_of_4?(s) that takes a string and returns true if the string
represents a binary number that is a multiple of 4. NOTE: be sure it returns false if the string
is not a valid binary number!
Implement a class BookInStock which represents a book with an ISBN
number, isbn, and price of the book as a floating-point number,
price, as attributes (instance variables).
The constructor should accept the ISBN number
(a string, since in real life ISBN numbers can begin with zero and can
include hyphens) as the first argument and price as second argument, and
should raise ArgumentError (one of Ruby's built-in exception types) if
the ISBN number is the empty string or if the price is less than or
equal to zero. Include the proper getters and setters for these
attributes.
Include a method price_as_string that returns the price of
the book formatted with a leading dollar sign and two decimal places, that is, a price
of 20 should format as "$20.00" and a price of 33.8 should format as
"$33.80".