Dotted pair structures

src/syntax/ast.rs

@@ -43,6 +43,7 @@ impl<T: Hash> Hash for Spanned<T> {
 pub enum Expr<'a> {
     List(Vec<Spanned<Self>>),
     Vector(Vec<Spanned<Self>>),
+    Pair((Box<Spanned<Self>>, Box<Spanned<Self>>)),
     Quote(Box<Spanned<Self>>),
     Symbol(Cow<'a, str>),
     Keyword(Cow<'a, str>),
@@ -58,6 +59,7 @@ impl<'a> Display for Expr<'a> {
                 write!(f, "#")?;
                 fmt_list(f, vec)
             }
+            Self::Pair((l, r)) => write!(f, "{l} . {r}"),
             Self::Quote(expr) => write!(f, "'{expr}"),
             Self::Symbol(sym) => write!(f, "{sym}"),
             Self::Keyword(kw) => write!(f, ":{kw}"),

src/syntax/lexer.rs

@@ -11,6 +11,9 @@ pub enum Token<'a> {
     #[token(")")]
     RightParen,
 
+    #[token(".")]
+    Dot,
+
     #[token("'")]
     Quote,
 
@@ -51,6 +54,7 @@ impl<'a> Display for Token<'a> {
         match self {
             Token::LeftParen => write!(f, "("),
             Token::RightParen => write!(f, ")"),
+            Token::Dot => write!(f, "."),
             Token::Quote => write!(f, "'"),
             Token::Octothrope => write!(f, "#"),
             Token::String(s) => write!(f, "\"{s}\""),