Module 1 Week 3 Diagnostic

week_3.markdown

Module 1 Week 3 Diagnostic

This exercise is intended to help you assess your progress with the concepts and techniques we've covered during the week.

For these questions, write a short snippet of code that meets the requirement. In cases where the question mentions a "given" data value, use the variable given to refer to it (instead of re-writing the information).

1. What does the following code output?

def print_variables(x)
  puts "x: #{x}"
  puts "b: #{b}"
end

def b
  12
end

a = 4
print_variables(a)

x: 4
b: 12

2. Working with files

Given a text file located at "~/Documents/pizza.txt", write code to read the file from the filesystem and print each line one at a time.

File.readlines("~/Documents/pizza.txt")

3. Writing Files

Given a text file located at "~/Documents/pizza.txt", write code to read the file from the filesystem, then write a new file at "~/Documents/line_count.txt" containing the number of lines in the original file.

lines = File.readlines("~/Documents/pizza.txt")

File.open("~/Documents/line_count.txt", "w") { |file| file.write(lines) }

4. Corgis

Imagine a simple ruby class designed to represent a Corgi dog. Write a test for each of the following features:

• A Corgi can be created with no arguments
• A Corgi can be assigned a name
• A Corgi can be asked for its name
• A Corgi can be asked for its posture, which should default to "standing"
• A Corgi can be asked to lie down, which should change its posture to "laying"

def test_it_can_be_created_with_no_arguements
  corgi = Corgi.new(name) #name argument is assigned to nil or default in class
  assert_instance_of corgi, corgi.class
end

def test_it_can_be_assigned_a_name
  corgi = Corgi.new("Carl")
  assert_equal "Carl", corgi.name
end

def test_it_can_be_asked_for_its_name
  corgi = Corgi.new("Carl")
  assert_equal "Carl", corgi.name?
end

def test_it_can_be_asked_for_posture
  corgi = Corgi.new("Carl")
  assert_equal "standing", corgi.posture?
end

def test_it_can_be_assigned_a_name
  corgi = Corgi.new("Carl")
  corgi.lie_down
  assert_equal "laying", corgi.posture?
end

5. Counting Words

Given an array of words ["dog", "cat", "gerbil", "cat", "hamster", "rabbit", "rabbit"], create a Hash containing the individual words as keys and the number of times the word appears in the list as values. That is:

animals.each_with_object(Hash.new(0)) { |word,counts| counts[word] += 1 }

{"dog" => 1, "cat" => 2, "gerbil" => 1, "hamster" => 1, "rabbit" => 2}

6. Reading Files

Given a text file located at "~/Documents/pizza.txt", write code to read the file from the filesystem, then process the file's lines so that:

• Even lines go into an array called even
• Odd lines go into an array called odd

(Assume the first line is numbered 0, and is thus even)

even = []
odd = []

lines = File.read(filename)
lines.each_with_index do |value, index|
  even << value if index.even?
  odd << value if index.odd?
end

7. Stacks

Given the following code, draw a simple diagram representing the stack frames that the program will generate as it is run. In order to show change in the stack over time, you may need to re-copy the lower frames into a new diagram.

def wrap_it(x)
  "<<<" + x + ">>>"
end

def string_it(x)
  x.to_s
end

def churn_it(x)
  wrap_it(string_it(x))
end


churn_it(10)