Expression

An Elixir library implementing the FLOIP Expressions language.

iex> Expression.evaluate("Hello @name", %{
  "name" => "World"
})
"Hello World"

iex> Expression.evaluate("Hello @contact.name", %{
  "contact" => %{
    "name" => "peter"
  }
})
"Hello peter"

iex> Expression.evaluate("Hello @contact.name, you were born in @(YEAR(contact.birthday))", %{
  "contact" => %{
    "name" => "mary",
    "birthday" => "1920-02-02T00:00:00"
  }
})
{:ok, "Hello mary, you were born in 1920"}

iex> Expression.evaluate("Hello @PROPER(contact.name)", %{
  "contact" => %{
    "name" => "peter rabbit"
  }
})
"Hello Peter Rabbit"

iex> Expression.evaluate("Your next appointment is @(EDATE(contact.appointment, 1))", %{
  "contact" => %{
    "appointment" => DateTime.utc_now()
  }
})
{:ok, "Your next appointment is 2021-01-02 12:38:14.426663Z"}

iex> Expression.evaluate("Your next appointment is @(DATEVALUE(EDATE(contact.appointment, 1), \"%Y-%m-%d\"))", %{
  "contact" => %{
    "appointment" => "2020-12-13T23:35:55"
  }
})
{:ok, "Your next appointment is 2021-01-13"}

iex> Expression.evaluate("Dear @IF(contact.gender = 'M', 'Sir', 'Client')", %{
  "contact" => %{
    "gender" => "O"
  }
})
{:ok, "Dear Client"}

See Engaged.Callbacks for all the functions implemented.

Types

Expression knows the following types:

iex> # Decimals
iex> Expression.evaluate("@(1.23)")
{:ok, #Decimal<1.23>}
iex> # Integers
iex> Expression.evaluate("@(1)")
{:ok, 1}
iex> # DateTime in ISO and a sloppy US formats
iex> Expression.evaluate("@(2020-12-13T23:35:55)")
{:ok, ~U[2020-12-13 23:35:55.0Z]}
iex> Expression.evaluate("@(13-12-2020 23:35:55)")
{:ok, ~U[2020-12-13 23:35:55Z]}
iex> # case insensitive booleans
iex> Expression.evaluate("@(true)")
{:ok, true}
iex> Expression.evaluate("@(TrUe)")
{:ok, true}
iex> Expression.evaluate("@(false)")
{:ok, false}
iex> Expression.evaluate("@(FaLsE)")
{:ok, false}

Future extensions

• It may be worth implementing a binary only expression parser, something that is guaranteed to only return a true or false. That could be useful when building decision trees with dynamic conditionals depending on context.

Installation

This is not available in Hex.pm or Hexdocs.pm yet

If available in Hex, the package can be installed by adding expression to your list of dependencies in mix.exs:

def deps do
  [
    {:expression, "~> 0.4.1"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/expression.