From fc8989a2019922208c1e054a7a08a44ed7db1a35 Mon Sep 17 00:00:00 2001
From: Case Duckworth
Date: Sun, 31 Mar 2024 22:14:22 -0500
Subject: Add quasiquote

---
 eval.lua | 44 +++++++++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/eval.lua b/eval.lua
index e13fb97..714c67e 100644
--- a/eval.lua
+++ b/eval.lua
@@ -48,17 +48,43 @@ function m.procedure (params, body, env)
 	return setmetatable(t, mt)
 end
 
-local specials = {
 m.specials = {
 	-- each of these takes R (a list of args) and E (an environment)
-	quote =
-		function (r, e) return r[1] end,
-	define =
-		function (r, e) rawset(e, r[1], m.eval(r[2][1], e)) end,
-	lambda =
-		function (r, e) return m.procedure(r[1], r[2], e) end,
-	["set!"] =
-		function (r, e) e[r[1]] = m.eval(r[2][1], e) end,
+	quote = function (r, e) return r[1] end,
+	quasiquote =
+		function (r, e)
+			local x = r[1]
+			if not type.islist(x) or x == type.null then
+				return x
+			end
+			local QQ, fin = {}, nil
+			local car, cdr = x[1], x[2]
+			while cdr do
+				if type.islist(car) then
+					if car[1] == "unquote" then
+						table.insert(QQ,
+							m.eval(car[2][1], e))
+					elseif car[1] == "unquote-splicing" then
+						local usl = m.eval(car[2][1], e)
+						if not type.islist(usl) then
+							fin = usl
+							break
+						end
+						while usl[2] do
+							table.insert(QQ, usl[1])
+							usl = usl[2]
+						end
+					end
+				else
+					table.insert(QQ, car)
+				end
+				car, cdr = cdr[1], cdr[2]
+			end
+			return type.list(QQ, fin)
+		end,
+	define = function (r, e) rawset(e, r[1], m.eval(r[2][1], e)) end,
+	lambda = function (r, e) return m.procedure(r[1], r[2], e) end,
+	["set!"] = function (r, e) e[r[1]] = m.eval(r[2][1], e) end,
 	["if"] =
 		function (r, e)
 			local test, conseq, alt =
-- 
cgit 1.4.1-21-gabe81