tuple splatterns now work

src/main.rs

@@ -55,28 +55,8 @@ use crate::base::*;
 
 pub fn main() {
     let src = "
-fn fancy_add {
-    () -> 0
-    (n as :number) -> n
-    (x as :number, y as :number) -> add (x, y)
-}
-
-fn fancy_sub {
-    () -> 0
-    (n as :number) -> n
-    (x as :number, y as :number) -> sub (x, y)
-}
-
-fn fib {
-   (1) -> 1
-   (2) -> 1
-   (n) -> fancy_add(
-       fib (fancy_sub (n, 1))
-       fib (fancy_sub (n, 2))
-   ) 
-}
-
-fib (30)
+let (x, y, ...z) = (1, 2, 3)
+z
     ";
     let (tokens, lex_errs) = lexer().parse(src).into_output_errors();
     if lex_errs.len() > 0 {

src/parser.rs

@@ -211,6 +211,7 @@ pub enum Pattern<'src> {
     Keyword(&'src str),
     Word(&'src str),
     As(&'src str, &'src str),
+    Splattern(Box<Spanned<Self>>),
     Placeholder,
     Tuple(Vec<Spanned<Self>>),
     List(Vec<Spanned<Self>>),
@@ -229,6 +230,7 @@ impl<'src> fmt::Display for Pattern<'src> {
             Pattern::Keyword(k) => write!(f, ":{}", k),
             Pattern::Word(w) => write!(f, "{}", w),
             Pattern::As(w, t) => write!(f, "{} as {}", w, t),
+            Pattern::Splattern(p) => write!(f, "...{}", (*p).0.to_string()),
             Pattern::Placeholder => write!(f, "_"),
             Pattern::Tuple(t) => write!(
                 f,
@@ -300,8 +302,24 @@ where
     }
     .map_with(|a, e| (a, e.span()));
 
+    let bare_splat = just(Token::Punctuation("...")).map_with(|_, e| {
+        (
+            Pattern::Splattern(Box::new((Pattern::Placeholder, e.span()))),
+            e.span(),
+        )
+    });
+
+    let splattable = word_pattern.clone().or(placeholder_pattern.clone());
+
+    let patt_splat = just(Token::Punctuation("..."))
+        .ignore_then(splattable)
+        .map_with(|x, e| (Pattern::Splattern(Box::new(x)), e.span()));
+
+    let splattern = patt_splat.or(bare_splat);
+
     let tuple_pattern = pattern
         .clone()
+        .or(splattern.clone())
         .separated_by(separators.clone())
         .allow_leading()
         .allow_trailing()
@@ -312,6 +330,7 @@ where
 
     let list_pattern = pattern
         .clone()
+        .or(splattern.clone())
         .separated_by(separators.clone())
         .allow_leading()
         .allow_trailing()

src/vm.rs

@@ -79,16 +79,32 @@ pub fn match_pattern<'src, 'a>(
         }
         // todo: add splats to these match clauses
         (Pattern::Tuple(x), Value::Tuple(y)) => {
-            if x.len() != y.len() {
+            let has_splat = x.iter().any(|patt| {
+                if let (Pattern::Splattern(_), _) = patt {
+                    true
+                } else {
+                    false
+                }
+            });
+            if x.len() > y.len() || (!has_splat && x.len() != y.len()) {
                 return None;
             };
             let to = ctx.len();
             for i in 0..x.len() {
-                if let None = match_pattern(&x[i].0, &y[i], ctx) {
-                    while ctx.len() > to {
-                        ctx.pop();
+                if let Pattern::Splattern(patt) = &x[i].0 {
+                    let mut list = Vector::new();
+                    for i in i..y.len() {
+                        list.push_back(y[i].clone())
+                    }
+                    let list = Value::List(list);
+                    match_pattern(&(*patt).0, &list, ctx);
+                } else {
+                    if let None = match_pattern(&x[i].0, &y[i], ctx) {
+                        while ctx.len() > to {
+                            ctx.pop();
+                        }
+                        return None;
                     }
-                    return None;
                 }
             }
             Some(ctx)
@@ -260,7 +276,9 @@ pub fn eval<'src, 'a>(
             let val = if let Some((_, value)) = ctx.iter().rev().find(|(name, _)| w == name) {
                 value.clone()
             } else {
-                unreachable!()
+                return Err(LudusError {
+                    msg: format!("unbound name {w}"),
+                });
             };
             Ok(val)
         }