ex_aequo

ExAequo Elixir Tools

Meaning of the name. All nice latin expressions starting with Ex are consumed at an alarming rate, so, all things being equal, I choose this one.

ExAequo.Enum offers some extension functions for Elixir's Enum module

Grouped Accumulation

Groupes accumulated values of an Enum according to a function that indicates if two consequent items are of the same kind and if so how to accumulate their two values.

The grouped_reduce function returns the groupes in reverse order, as, during traversal of lists quite often reversing the result of the classical "take first and push a function of it to the result" pattern cancels out.

An optional, reverse: true keyword option can be provided to reverse the final result for convenience.

  iex> add_same = fn {x, a}, {y, b} ->
  ...>               cond do
  ...>                 x == y -> {:cont, {x, a + b}}
  ...>                 true   -> {:stop, nil} end end
  ...> E.grouped_reduce(
  ...>   [{:a, 1}, {:a, 2}, {:b, 3}, {:b, 4}], add_same)
  [{:b, 7}, {:a, 3}]

The grouped_inject function behaves almost identically to grouped_reduce, however an initial value is provided.

  iex> sub_same = fn {x, a}, {y, b} -> 
  ...>               cond do
  ...>                 x == y -> {:cont, {x, a - b}}
  ...>                 true   -> {:stop, nil}
  ...>               end
  ...>            end
  ...> E.grouped_inject(
  ...> [{:a, 1}, {:b, 2}, {:b, 2}, {:c, 2}, {:c, 1}, {:c, 1}],
  ...>  {:a, 43}, sub_same, reverse: true)
  [a: 42, b: 0, c: 0]