The document shows examples of pattern matching, case expressions, macros, and queries in Elixir. It demonstrates matching on different data types like lists, maps, tuples, and structs. It also shows examples of macros, case expressions, queries, and defining functions with pattern matching.

2. |>

3. Treat.give(Dog.find(dog_id))
dog_id
|> Dog.find()
|> Treat.give()

4. new_email(
to: "foo@example.com",
from: "me@example.com",
subject: "Welcome!!!",
html_body: "<strong>Welcome</strong>",
text_body: "welcome"
)

5. new_email
|> to("foo@example.com")
|> from("me@example.com")
|> subject("Welcome!!!")
|> html_body("<strong>Welcome</strong>")
|> text_body("welcome")

7. x = 1 # this is the "match" operator
1 = x # this is completely legit
# lists
[a, b, c] = [1, 2, 3]
# maps
%{id: id} = %{id: 1}
%{id: id} = %{id: 1, name: "fido"}
%{id: id} = %User{id: 1} # structs work too!
# tuples
{:ok, status, response} = {:ok, 200, "<h1>Dogs</h1>"}

8. {:ok, response} = HTTP.get("/dogs")

9. case HTTP.get("/dogs") do
{:ok, response} ->
Logger.info(response)
{:error, error} ->
Logger.error(error)
end

10. defmodule DogService do
def run do
HTTP.get("/doggies")
end
def log({:ok, response}) do
Logger.info(response)
end
def log({:error, error}) do
Logger.error(error)
end
def log(_) do
Logger.error("uhh... what happened?")
end
end
DogService.run |> DogService.log

12. def give_treat(dog) do
if dog do
if dog.age > 5
"here ya go, #{dog.name}"
else
"here ya go, pup"
end
else
"uhhh... no dog?"
end
end

13. def give_treat(nil), do: "uhh... no dog?"
def give_treat(%{name: name, id: id}) when id > 5 do
"here ya go, #{name}"
end
def give_treat(_) do
"here ya go, pup"
end

14. def give_treat(nil), do: "uhh... no dog?"
def give_treat(id) when is_integer(id) do
id |> find |> give_treat
end
def give_treat(%{age: age, name: name}) when age > 5 do
"here ya go, #{name}"
end
def give_treat(_) do
"here ya go, pup"
end

16. case DB.insert(changeset) do
{:ok, record} ->
# woot woot!
{:error, :timeout} ->
# handle it
{:error, changeset} ->
# handle it
end

18. def save(changeset) do
case DB.insert(changeset) do
{:ok, record} ->
case ElasticSearch.sync(record) do
{:ok, _, response} ->
{:ok, record, response}
{:error, status, response} ->
{:error, status, response}
end
{:error, error} ->
{:error, error}
end
end

19. with {:ok, record} <- DB.insert(changeset),
{:ok, _, response} <- ElasticSearch.sync(record),
do: {:ok, record, response}

21. iex> quote do: sum(1, 2, 3)
{:sum, [], [1, 2, 3]}

22. iex> Macro.to_string(quote do: sum(1, 2 + 3, 4))
"sum(1, 2 + 3, 4)"

23. iex> number = 13
iex> Macro.to_string(quote do: 11 + number)
"11 + number"
iex> number = 13
iex> Macro.to_string(quote do: 11 + unquote(number))
"11 + 13"

24. assert "foo" =~ "bar"
Assertion with =~ failed
code: "foo" =~ "bar"
lhs: "foo"
rhs: "bar"

25. defmodule Example do
def iif(test, a, b) do
if test, do: a, else: b
end
end
Example.iif(false, IO.puts("a"), IO.puts("b"))
Example.iif(true, IO.puts("a"), IO.puts("b"))

26. a
b
a
b

27. defmodule Example do
defmacro iif(test, a, b) do
quote do
if unquote(test), do: unquote(a), else: unquote(b)
end
end
end
Example.iif(false, IO.puts("a"), IO.puts("b"))
Example.iif(true, IO.puts("a"), IO.puts("b"))

28. b
a

29. from fish in Fish,
join: fisherman in assoc(fish, :fisherman),
group_by: fisherman.name,
select: [max(fish.length), fisherman.name]