public void Should_evaluate_expression_with_user_defined_functions_and_variables()
{
// Given
var context = new Context()
.SetVariable("G", 6.67428D)
.SetVariable("earth_mass", Evaluate.As <double>("5.97219 * pow(10,24)")) // 5.97219E+24 kg
.SetVariable("lunar_mass", Evaluate.As <double>("7.34767309 * pow(10,22)")) // 7.34767309E+22 kg
.SetVariable("perigee_dist", 356700000D) // moon-earth distance at perigee in m
.SetFunction("calc_force", args => (
TypeConverter.ToNumber(args[0]) * TypeConverter.ToNumber(args[1]) / Math.Pow(TypeConverter.ToNumber(args[2]), 2)));
// When
var result = context.EvaluateAs <double>("G * calc_force(earth_mass, lunar_mass, perigee_dist)");
// Than
result.Should().Be(2.3018745174107073E+31D);
}