Case in

About Case

case is a control flow structure that allows us to compare a given value against many patterns. Clauses in a case expression are evaluated from top to bottom, until a match is found.

In many cases, using case is interchangeable with defining multiple function clauses. Pattern matching and guards can be used in case clauses.

# one function clause, multiple case clauses
def age_group(age) do
  case age do
    0 -> ~c"infant"
    age when age < 4 -> ~c"baby"
    age when age < 13 -> ~c"child"
    age when age < 18 -> ~c"teenager"
    _ -> ~c"adult"
  end
end

# multiple function clauses, no case
def age_group(0), do: ~c"infant"
def age_group(age) when age < 4, do: ~c"baby"
def age_group(age) when age < 13, do: ~c"child"
def age_group(age) when age < 18, do: ~c"teenager"
def age_group(_), do: ~c"adult"

There are no strict rules for choosing one over the other. It's a matter of personal preference that usually depends on context.