Settings View Source Code Execution

We can execute code in rules. This may be useful in the following scenarios:

• The output of a rule is not literal but should be calculated based on the input.
• One input field's value is based on another.

Currently (v0.1.0), we only support execution in output fields.

security-warning

Security Warning

Use this feature with extreme caution! Never trust inputs from users.

syntax

Syntax

Code is wrapped in a "`" pair, e.g.

iex> table = Tablex.new("""
...>   F x   || abs
...>   1 >=0 || `x`
...>   2 <0  || `-x`
...>   """)
...>
...> Tablex.decide(table, x: -42)
%{abs: 42}

restriction

Restriction

The code is in raw Elixir format but not all syntax tokens are allowed to use. It follows the default restriction of formular.

For example, the following code is not allowed:

MyApp.foo() because it is not supported to invoke "." operation.

variables

Variables

We can refer to arbitary variable names as long as are provided in the binding argument of Tablex.decide/2 or Tablex/decide/3. For example:

iex> table = Tablex.new("""
...>   M day_of_week || "Go to Library"  Volunteer  Blogging
...>   1 1           || T                -          -
...>   2 2           || F                T          -
...>   3 -           || F                F          `week_of_month == 4`
...>   """)
...>
...> Tablex.decide(table, day_of_week: 1, week_of_month: 4)
%{go_to_library: true, volunteer: false, blogging: true}

Note that week_of_month is not an input field but a bound variable on execution.

functions

Functions

Functions are supported through formular's custom function.

Example:

iex> defmodule MyFib do
...>   @table Tablex.new("""
...>     F x   || fib
...>     1 0   || 0
...>     2 1   || 1
...>     3 >=2 || `fib(x - 1) + fib(x - 2)`
...>     """)
...>
...>   def fib(x) when is_integer(x) and x >= 0 do
...>     %{fib: y} = Tablex.decide(@table, [x: x], context: __MODULE__)
...>     y
...>   end
...> end
...>
...> MyFib.fib(5)
5