module Chervil
  RSpec.describe AST::Application do
    it 'evaluates addition' do
      env = Env.new
      expect(
        AST::Application.new(
          AST::Identifier.new('+'),
          [AST::Number.new(1.0), AST::Number.new(2.0)]
        )
          .evaluate(env)
      ).to eq(3.0)
    end

    it 'evaluates nested arithmetic' do
      env = Env.new
      expect(
        AST::Application.new(
          AST::Identifier.new('+'),
          [
            AST::Application.new(
              AST::Identifier.new('+'),
              [AST::Number.new(1.0), AST::Number.new(2.0)]
            ),
            AST::Application.new(
              AST::Identifier.new('+'),
              [AST::Number.new(3.0), AST::Number.new(4.0)]
            )
          ]
        )
          .evaluate(env)
      ).to eq(10.0)
    end

    it 'returns an error if the function is not defined' do
      env = Env.new
      expect(AST::Application.new(AST::Identifier.new("x"), []).evaluate(env)).to eq(
        Error.new("Unbound variable x")
      )
    end
  end
end