wisp/src/syntax/ast.rs

use ordered_float::OrderedFloat;
use std::{
    borrow::Cow,
    fmt::{Display, Write},
};

/// A Wisp AST
#[derive(Debug, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub enum Expr<'a> {
    List(Vec<Self>),
    Vector(Vec<Self>),
    Map(Vec<(Self, Self)>),
    Symbol(Cow<'a, str>),
    Keyword(Cow<'a, str>),
    Number(OrderedFloat<f64>),
    String(Cow<'a, str>),
}

impl<'a> Display for Expr<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::List(list) => write_seq(f, list, "(", ")"),
            Self::Vector(vec) => write_seq(f, vec, "[", "]"),
            Self::Map(map) => write_seq(f, map.iter().map(|(k, v)| format!("{k} {v}")), "[", "]"),
            Self::Symbol(sym) => write!(f, "{sym}"),
            Self::Keyword(kw) => write!(f, ":{kw}"),
            Self::Number(n) => write!(f, "{n}"),
            Self::String(s) => write!(f, "\"{s}\""),
        }
    }
}

fn write_seq(
    f: &mut impl Write,
    iterable: impl IntoIterator<Item = impl Display>,
    delimiter_left: &str,
    delimiter_right: &str,
) -> std::fmt::Result {
    let mut iter = iterable.into_iter();
    write!(f, "{delimiter_left}")?;
    if let Some(x) = iter.next() {
        write!(f, "{x}")?;
    }
    for x in iter {
        write!(f, " {x}")?;
    }
    write!(f, "{delimiter_right}")
}