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.open("~/Documents/pizza.txt").readlines.each do |line|
  puts line
end

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.

total_lines = 0
pizza = File.open("example.txt").readlines.each do |line|
  puts line
  total_lines += 1
end

File.write("pizza.txt", "The number of lines is #{total_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"

require "./corgi"
require 'minitest/autorun'
require 'minitest/pride'

class CorgiTest < Minitest::Test

  def test_corgi_exists
    corgi = Corgi.new
    assert_instance_of Corgi, corgi
  end

  def test_corgi_has_a_name
    corgi = Corgi.new("Bob")
    assert_equal "Bob", corgi.name
  end

  def test_corgi_can_be_asked_for_name
    corgi = Corgi.new("Bob")
    assert_equal "My name is Bob", corgi.name?
  end

  def test_corgi_can_be_asked_for_posture
    corgi = Corgi.new("Bob")
    assert_equal "standing", corgi.posture
  end

  def test_corgi_can_lie_down
    corgi = Corgi.new("Bob")
    corgi.lay_down
    assert_equal "laying", corgi.posture
  end

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

animal_bank = {}
animals.each do |animal|
  animal_bank[animal] = animals.count(animal)
end

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)

line_num = 0
even = []
odd = []
evens_and_odds = File.open("pizza.txt").readlines.map do |line|
  even << line if line_num % 2 == 0
  odd << line if line_num % 2 != 0
  line_num += 1
end
p even
p odd

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)

<<<10>>>
wrap_it(10.to_s)
string_it(10)
churn_it(10)