use super::ExpressionTrait;

#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Expression {
    Variable(usize),
    Abstraction(Box<Expression>),
    Application(Box<Expression>, Box<Expression>),
}

impl ExpressionTrait for Expression {
    fn variable(index: usize) -> Self {
        Expression::Variable(index)
    }

    fn abstraction(body: Self) -> Self {
        Expression::Abstraction(Box::new(body))
    }

    fn application(l: Self, r: Self) -> Self {
        Expression::Application(Box::new(l), Box::new(r))
    }
}