From 827e54124f03fd11d497caa8213ca583f480b982 Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Fri, 2 Apr 2021 11:05:11 +0530
Subject: add DottedList type, fix `cons` finally

---
 src/lisp/expr.rs | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

(limited to 'src/lisp/expr.rs')

diff --git a/src/lisp/expr.rs b/src/lisp/expr.rs
index 31476c9..aeaa2d8 100644
--- a/src/lisp/expr.rs
+++ b/src/lisp/expr.rs
@@ -62,6 +62,7 @@ pub enum LispExpr {
     Unit,
     Number(LispNumber),
     List(Vec<LispExpr>),
+    DottedList(Vec<LispExpr>),
     StringLit(String),
     BoolLit(bool),
     Ident(Ident),
@@ -157,7 +158,14 @@ impl LispExpr {
     pub fn unwrap_list(&self) -> Vec<LispExpr> {
         match &self {
             LispExpr::List(p) => p.clone(),
-            _ => panic!("attempt to call `unwrap_number` on invalid type"),
+            _ => panic!("attempt to call `unwrap_list` on invalid type"),
+        }
+    }
+
+    pub fn unwrap_dotted_list(&self) -> Vec<LispExpr> {
+        match &self {
+            LispExpr::DottedList(p) => p.clone(),
+            _ => panic!("attempt to call `unwrap_dotted_list` on invalid type"),
         }
     }
 
@@ -209,6 +217,13 @@ impl fmt::Display for LispExpr {
                     &l.iter().map(|expr| format!("{}", expr)).collect::<Vec<_>>()[..].join(" ")
                 )?;
             }
+            LispExpr::DottedList(l) => {
+                write!(f, "(")?;
+                for item in &l[..l.len() - 1] {
+                    write!(f, "{} ", item)?;
+                }
+                write!(f, ". {})", &l[l.len() - 1])?;
+            }
             LispExpr::StringLit(s) => write!(f, "{:?}", s)?,
             LispExpr::Char(c) => write!(f, "{}", c)?,
             LispExpr::BoolLit(b) => {
@@ -237,7 +252,14 @@ impl fmt::Debug for LispExpr {
         match self {
             LispExpr::Unit => f.debug_tuple("Unit").finish(),
             LispExpr::Number(n) => write!(f, "Number({:?})", n),
-            LispExpr::List(l) => f.debug_list().entries(l.iter()).finish(),
+            LispExpr::List(l) => {
+                write!(f, "List ")?;
+                f.debug_list().entries(l.iter()).finish() 
+            },
+            LispExpr::DottedList(l) => {
+                write!(f, "DottedList ")?;
+                f.debug_list().entries(l.iter()).finish() 
+            },
             LispExpr::StringLit(s) => write!(f, "String({:?})", s),
             LispExpr::Char(c) => write!(f, "Char({:?})", c),
             LispExpr::BoolLit(b) => write!(f, "Bool({:?})", b),
-- 
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