use super::Identifier;
#[derive(Clone, Debug, PartialEq)]
pub enum Expr {
Variable(Identifier),
Symbol(Identifier),
Apply { lhs: Box<Expr>, rhs: Box<Expr> },
Lambda { param: Identifier, body: Box<Expr> },
}
impl From<&str> for Expr {
fn from(s: &str) -> Self {
match s.chars().nth(0) {
Some(':') => Expr::Symbol((&s[1..]).into()),
Some(_) => Expr::Variable(s.into()),
_ => panic!("invalid identifier"),
}
}
}
impl From<String> for Expr {
fn from(s: String) -> Self {
s.as_str().into()
}
}
pub fn v<Id: Into<Identifier>>(id: Id) -> Expr {
Expr::Variable(id.into())
}
pub fn s<Id: Into<Identifier>>(id: Id) -> Expr {
Expr::Symbol(id.into())
}
pub fn a<L: Into<Expr>, R: Into<Expr>>(lhs: L, rhs: R) -> Expr {
Expr::Apply {
lhs: Box::new(lhs.into()),
rhs: Box::new(rhs.into()),
}
}
pub fn l<P: Into<Identifier>, B: Into<Expr>>(param: P, body: B) -> Expr {
Expr::Lambda {
param: param.into(),
body: Box::new(body.into()),
}
}