Trait egg::FromOp[−][src]

pub trait FromOp: Language + Sized {
    type Error: Debug;
    fn from_op(op: &str, children: Vec<Id>) -> Result<Self, Self::Error>;
}

Expand description

A trait for parsing e-nodes. This is implemented automatically by define_language!.

If a Language implements both Display and FromOp, the Display implementation should produce a string suitable for parsing by from_op:

fn from_op_display_compatible<T: FromOp + Display>(node: T) {
    let op = node.to_string();
    let mut children = Vec::new();
    node.for_each(|id| children.push(id));
    let parsed = T::from_op(&op, children).unwrap();

    assert_eq!(node, parsed);
}

Examples

define_language! implements FromOp and Display automatically:


define_language! {
    enum Calc {
       "+" = Add([Id; 2]),
       Num(i32),
    }
}

let add = Calc::Add([Id::from(0), Id::from(1)]);
let parsed = Calc::from_op("+", vec![Id::from(0), Id::from(1)]).unwrap();

assert_eq!(add.to_string(), "+");
assert_eq!(parsed, add);