From cf430149b8e7317eceb8ac0f36e7b5f7d32a8bdb Mon Sep 17 00:00:00 2001
From: Case Duckworth
Date: Thu, 21 Mar 2024 22:42:13 -0500
Subject: Revert "Refactor eval"

This reverts commit 1d5041ff7bf92458d6d07ac6a03f2747dce9b9b1.
---
 eval.lua | 75 +++++++++++++++++++++++-----------------------------------------
 1 file changed, 27 insertions(+), 48 deletions(-)

diff --git a/eval.lua b/eval.lua
index 39a5bbe..9b1c315 100644
--- a/eval.lua
+++ b/eval.lua
@@ -1,12 +1,13 @@
 --- lam.eval
 
+local eval = {}
 local base = require "base"
 local type = require "type"
 local isNull, isList, isa, List, Cons =
 	type.isNull, type.isList, type.isa, type.List, type.Cons
 local unpack = table.unpack or unpack
 
-local function Env (inner, outer)
+function eval.Env (inner, outer)
 	local mt = {
 		__type = "Environment",
 		__index = outer,
@@ -24,7 +25,7 @@ local function Env (inner, outer)
 	return setmetatable(inner, mt)
 end
 
-local function Proc (params, body, env)
+function eval.Proc (params, body, env)
 	local v = {
 		params = params,
 		body = body,
@@ -41,51 +42,18 @@ local function Proc (params, body, env)
 					p, a = p.cdr, a.cdr
 				end
 				local b = self.body
-				local e = Env(inner, self.env)
+				local e = eval.Env(inner, self.env)
 				while not isNull(b.cdr) do
-					eval(b.car, e)
+					eval.eval(b.car, e)
 					b = b.cdr
 				end
-				return eval(b.car, e)
+				return eval.eval(b.car, e)
 			end,
 	}
 	return setmetatable(v, mt)
 end
 
-local specials = {
-	quote =
-		function (args, env)
-			return args.car
-		end,
-	define =
-		function (args, env)
-			rawset(env, args.car, eval(args.cdr.car, env))
-			return nil
-		end,
-	lambda =
-		function (args, env)
-			return Proc(args.car, args.cdr, env)
-		end,
-	["set!"] =
-		function (args, env)
-			env[args.car] = eval(args.cdr.car, env)
-			return nil
-		end,
-	["if"] =
-		function (args, env)
-			local test, conseq, alt =
-				args.car, args.cdr.car, args.cdr.cdr.car
-			if eval(test)
-			then return eval(conseq)
-			else return eval(alt)
-			end
-		end,
-}
--- Aliases
-specials.lam = specials.lambda
-specials.def = specials.define
-
-local function eval (x, env)
+function eval.eval (x, env)
 	env = env or base.env
 	if isa(x, "Symbol") then
 		return env[x]
@@ -93,14 +61,29 @@ local function eval (x, env)
 		return x
 	else
 		local op, args = x.car, x.cdr
-		if specials[op] then
-			return specials[op](args, env)
+		if op == "quote" then
+			return args.car
+		elseif op == "define" or op == "def" then
+			rawset(env, args.car, eval.eval(args.cdr.car, env))
+			return nil
+		elseif op == "set!" then
+			env[args.car] = eval.eval(args.cdr.car, env)
+		elseif op == "lambda" or op == "lam" then
+			return eval.Proc(args.car, args.cdr, env)
+		elseif op == "if" then
+			assert(not isNull(args.cdr), "Malformed 'if'")
+			local test, conseq, alt =
+				args.car, args.cdr.car, args.cdr.cdr.car
+			if eval.eval(test)
+			then return eval.eval(conseq)
+			else return eval.eval(alt)
+			end
 		else		-- procedure
-			local proc = eval(op, env)
+			local proc = eval.eval(op, env)
 			local params = {}
 			local a = args
 			while a.cdr do
-				table.insert(params, eval(a.car, env))
+				table.insert(params, eval.eval(a.car, env))
 				a = a.cdr
 			end
 			return proc(List(params))
@@ -109,8 +92,4 @@ local function eval (x, env)
 end
 
 ---
-return {
-	Env = Env,
-	Proc = Proc,
-	eval = eval,
-}
+return eval
-- 
cgit 1.4.1-21-gabe81