use crate::*;

pub trait DslNs<'a, T: 'a>: DslNsWords<'a, T> + DslNsExprs<'a, T> {
    /// Resolve an expression or symbol.
    fn from (&'a self, dsl: impl Dsl + 'a) -> Perhaps<T> {
        if let Ok(Some(literal)) = self.from_literal(&dsl) {
            Ok(Some(literal))
        } else if let Ok(Some(meaning)) = self.from_word(&dsl) {
            Ok(Some(meaning))
        } else {
            self.from_expr(dsl)
        }
    }
    /// Resolve as literal if valid.
    fn from_literal (&self, _: impl Dsl) -> Perhaps<T> {
        Ok(None)
    }
}