EvalEx

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EvalEx is a powerful expression evaluation library for Elixir, based on evalexpr using rustler.

About

EvalEx evaluates expressions in Elixir, leveraging the evalexpr crate tiny scripting language.

Please refer to the evalexpr documentation for extended information about the language.

Installation

Add :evalex to the list of dependencies in mix.exs:

def deps do
  [
    {:evalex, "~> 0.1.1"}
  ]
end

Usage

iex> EvalEx.eval("1 + 1")
{:ok, 2}

iex> EvalEx.eval("a * b", %{"a" => 10, "b" => 10})
{:ok, 100}

iex> EvalEx.eval("a == b", %{"a" => "tonio", "b" => "wanda"})
{:ok, false}

iex> EvalEx.eval("a != b", %{"a" => "tonio", "b" => "wanda"})
{:ok, true}

iex> EvalEx.eval("len(a)", %{"a" => [1, 2, 3]})
{:ok, 3}

iex> EvalEx.eval("a + b", %{"a" => 10})
{:error,
 {:variable_identifier_not_found,
  "Variable identifier is not bound to anything by context: \"b\"."}}

Precompile expressions

EvalEx allows you to precompile expressions to speed up the evaluation.

iex> {:ok, precompiled_expression} = EvalEx.precompile_expression("1 + 1")
{:ok,
 %EvalEx.PrecompiledExpression{
   reference: #Reference<0.2278913865.304611331.189837>,
   resource: #Reference<0.2278913865.304742403.189834>
 }}

iex> EvalEx.eval(precompiled_expression)
{:ok, 2}

Type conversion table

Elixir Types are converted to EvalEx types (and back) as follows:

Elixir EvalEx
integer() Int
float() Float
bool() Boolean
String.t() String
list() Tuple
tuple() Tuple
nil() Empty
pid() Empty (not supported)
ref() Empty (not supported)
fun() Empty (not supported)
map() Empty (not supported)

Rustler precompiled

By default, you don’t need the Rust toolchain installed because the lib will try to download a precompiled NIF file. In case you want to force compilation set the EVALEX_FORCE_BUILD environment variable to true or 1.

Precompiled NIFs are available for the following platforms:

License

This library is licensed under Apache 2.0 License. See LICENSE for details.

Links