True that, but I struggled to find a better name to be short and self-explanatory. OTOH, I do not want to miss the opportunity to return what was indeed validated on success.

Maybe I should go with validate/1 to return what valid?/1 currently returns and valid?/1 to return boolean.

As I continue working on Exvalibur, I have implemented custom guards and pattern matching of values.

I just blogged about how I used custom sigils to allow quoted expressions in the rules.

For what it’s worth, here’s the convention about trailing question marks and boolean return values: https://hexdocs.pm/elixir/master/naming-conventions.html#trailing-question-mark-foo

Starting with v0.8.0 Exvalibur accepts module-based validatiors:

defmodule Validator do
  use Exvalibur, rules: [
    %{
      matches: %{currency_pair: <<"EUR", _ :: binary>>},
      conditions: %{foo: %{min: 0, max: 100}},
      guards: %{num: num > 0 and num < 100}}]
end

Validator.valid?(%{currency_pair: "EURUSD", foo: 50, num: 50})
#⇒ {:ok, %{currency_pair: "EURUSD", foo: 50, num: 50}}
Validator.valid?(%{currency_pair: "USDEUR", foo: 50, num: 50})
#⇒ :error

I tend to think that there is a convention that functions with ? should return boolean type