control_flow_answer.ex

# Create a variable has_seen_star_wars and set it to true.
has_seen_star_wars = true

# Write code that prints "Ready for class" if you have seen at least one Star Wars movie (has_seen_star_wars).
if has_seen_star_wars do
  IO.puts "Ready for class"
end

# Flip has_seen_star_wars to false.
has_seen_star_wars = false

# Write code that prints "Ready for class" if you have seen at least one Star Wars movie (has_seen_star_wars). Otherwise print "Not ready".
if has_seen_star_wars do
  IO.puts "Ready for class"
else
  IO.puts "Not ready"
end

# Set the variable i_am_a_fan based on the if expression.
i_am_a_fan = if has_seen_star_wars do
               true
             else
               false
             end

# or more simply 
i_am_a_fan = has_seen_star_wars

# Set the variable inside the if expression. What happens? Why? Should you do this?
if has_seen_star_wars do
  i_am_a_fan = true
else
  i_am_a_fan = false
end

# Set the variable to the return value of the if expression. What happens? Why? Should you do this?
i_am_a_fan = if has_seen_star_wars do
               true
             else
               false
             end

# case examples

# bad
case has_seen_star_wars do
  true -> i_am_a_fan = true
  _ -> i_am_a_fan = false
end

# good
i_am_a_fan = case has_seen_star_wars do
  true -> true
  _ -> false
end

# cond examples

# bad
cond do
  has_seen_star_wars == true -> i_am_a_fan = true
  true -> i_am_a_fan = false
end

# good
i_am_a_fan = cond do
  has_seen_star_wars == true ->  true
  true -> false
end

# Write a function that will raise an error depending on the inputs.
defmodule MyModule do
  def my_fun(a,b) do
    a / b
  end
end

# Call the function and trigger the error.
MyModule.my_fun(10,0)

# Call the function and do not trigger the error.
MyModule.my_fun(10,2)

# Add error handling to the function so it does not fail if an error occurs.
defmodule MyModule do
  def my_fun(a,b) do
    try do
      a / b
    rescue 
      e in [ArithmeticError] -> 0
    end
  end
end

# Write a function that always prints out "Star Wars is awesome" even if it raises an error.
defmodule MyModule do
  def my_fun(a,b) do
    try do
      a / b
    after 
      IO.puts "Star Wars is awesome"
    end
  end
end

# Write a function that raises an error, handles it and logs the stacktrace in a friendly manner.
require Logger
defmodule MyModule do
  def my_fun(a,b) do
    try do
      a / b
    rescue 
      e in [ArithmeticError] -> 
        s = System.stacktrace
        friendly_stack = Exception.format_stacktrace(s)
        Logger.error("Sadly, an arithmetic error has occurred. #{friendly_stack}")
        0
    end
  end
end