Day03

Lessons Learned

• There was a lot of struggle with a misunderstanding that all structures are immutable. The documentation has instructions for updating a Map with Map.put or %{mymap| a: "value"}, but this is an illusion. Those function are returning a new map that needs to be assigned to a variable e.g., mymap = %{myap | a: "value"}.
• There was also a struggle with scoping. One cannot update a variable external to a block. For instance, if you have mymap = %{ a: "value"}, and entered an if statement and update the map mymap = %{mymap | a: "updated"} you can use the updated mymap , but once exiting the block (a.k.a if statement) the original value %{ a: "value"} will return.
• Decomposing the tuple is nice once you know how to do it.

  with {:ok, data} <- Day03.extract_first_number_range("467..114..") do
    assert data.substring == "467"
    assert data.indices == {0,3}
  else
    {:error, msg} -> raise msg
  end
  

• Little misunderstanding with the return: :index

  indices = Regex.run(~r/\d+/, str, return: :index)
  # The first time through it return the indices in order {0,3}. 
  # The second run through, it is reversed, {5, 3} <<< my misunderstanding.
  # The result is {index, length}
  

• Make sure you are solving the right problem

Day02

Lessons Learned

• I had a problem with an Enum.all? result always returning false for the comparision function: parse_pull_result. There were unit tests that passed successfully and examples working fine. It turned out, that even though I had a type defined it was allowing a string to be set where an integer should be. This doesn't show up in printing the values unless you wrap the values in "#{inspect(value)}" and then it showed the quotes around the integer.
• Setup the debugger does work with vscode
• Needed to enable the 'format on save' in VSCode for the editor
• Used type definitions to define struct fields
• Used spec to define method signatures with types
  • It is really easy to copy and paste a method definition and spec and forget to change one name or the other.
• An accumlator cannot be defined outside of the Enum.reduce function. It must be defined in the Enum.reduce function call.

Day01

Lessons Learned

• There was a lot of learning regarding syntax, Enum, Regex, and String functions.
• String concatenation uses <>, but a string with evaluations also works e.g.,"key: #{value}"
• The compiler is not going to give you the error messages you want.

Testing

# Execute the tests
mix test