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
4

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.

input = File.read("~/Documents/pizza.txt") File.open("~/Documents/line_count.txt", 'w'){|file| file.write(input.length)} 

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"

``` ruby

def test_no_args corgi = Corgi.new

assert_instance_of Corgi, corgi end def test_takes_a_name name = "Kristaps" corgi = Corgi.new(name)

assert_equal "Kristaps", corgi.name end def test_gives_name name = "Kristaps" corgi = Corgi.new(name)

assert_equal "My name is Kristaps", corgi.give_name end

def_test_gives_default_posture name = "Kristaps" corgi = Corgi.new(name, posture)

assert_equal "standing", corgi.posture end

def test_gives_posture_input name = "Kristaps" posture = "Laying" corgi = Corgi.new(name, posture)

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:

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

```ruby
animals = Hash.new(0) array.each { |animal| counts[animal] += 1 }

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)

input = File.readlines("~/Documents/pizza.txt") even = [] odd = []

input.each_with_index do |line, index| if line[index] % 2 even << line else odd << line end 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)