ExPression
Evaluate user input expressions.
Installation
The package can be installed by adding ex_pression to your list of dependencies in mix.exs:
def deps do
[
{:ex_pression, "~> 0.5.0"}
]
endKey features
- Safe evaluation without access to other Elixir modules.
iex> ExPression.eval("exit(self())")
{:error, %ExPression.Error{name: "UndefinedFunctionError", message: "Function 'self/0' was referenced, but was not defined", data: %{function: :self}}}- Support for JSON syntax and data types.
iex> ExPression.eval("""
{
"name": "ex_pression",
"deps": ["xpeg"]
}
""")
{:ok, %{"name" => "ex_pression", "deps" => ["xpeg"]}}- Familiar python-like operators and standard functions.
iex> ExPression.eval(~s/{"1": "en", "2": "fr"}[str(int_code)]/, bindings: %{"int_code" => 1})
{:ok, "en"}- Extend expressions by providing Elixir module with functions that you want to use.
defmodule MyFunctions do
# use $ special symbol in expressions
def handle_special("$", date_str), do: Date.from_iso8601!(date_str)
# Use diff function in expressions
def diff(date_1, date_2), do: Date.diff(date_1, date_2)
end
iex> ExPression.eval(~s/diff($"2023-02-02", $"2022-02-02")/, functions_module: MyFunctions)
{:ok, 365}Full language description can be found in FULL_DESCRIPTION.md
Implementation
String representation of expression is parsed into AST form. Parsing is done with PEG grammar parser xpeg. Grammar is defined in module ExPression.Parser.Grammar.
AST interpretation logic is written in plain Elixir in module ExPression.Interpreter.
Contribution
Feel free to make a pull request. All contributions are appreciated!
