mod operator;
mod function;
mod evaluate;

pub use self::evaluate::evaluate;

#[derive(Debug)]
pub enum EvalError {
	BadMath,
	TooBig,
	ZeroDivision,
	IncompatibleUnit,
	IncompatibleUnits(String, String),
	Undefined(String),
	EvaluationError,
	BadArguments(String, usize, usize)
}


impl ToString for EvalError {
	fn to_string(&self) -> String {
		match self {
			EvalError::BadMath => {
				String::from("Failed to evaluate expression")
			},
			EvalError::TooBig => {
				String::from("Number too big")
			},
			EvalError::ZeroDivision => {
				String::from("Division by zero")
			},
			EvalError::IncompatibleUnit => {
				String::from("Incompatible unit")
			},
			EvalError::IncompatibleUnits(a, b) => {
				format!("Incompatible units ({a} and {b})")
			},
			EvalError::Undefined(s) => {
				format!("{s} is undefined")
			},
			EvalError::EvaluationError => {
				String::from("Could not evaluate")
			},
			EvalError::BadArguments(s, want, got) => {
				format!("{s} takes {want} argument{}, got {got}",
					if *want == 1 {""} else {"s"},
				)
			}
		}
	}
}