Break special forms out into their own table

author: Case Duckworth 2024-03-23 15:51:07 -0500
committer: Case Duckworth 2024-03-23 15:51:27 -0500
commit: 4fb6e90474c8e9292df1a6210b8de260dd253ccb (patch)
tree: ae56acdb2d090ed36184b36635f41b692a652188
parent: Add a bunch of base functions (diff)
download: lam-4fb6e90474c8e9292df1a6210b8de260dd253ccb.tar.gz
lam-4fb6e90474c8e9292df1a6210b8de260dd253ccb.zip
1 files changed, 36 insertions, 17 deletions
diff --git a/eval.lua b/eval.lua
index 9b1c315..610b902 100644
--- a/eval.lua
+++ b/eval.lua

@@ -53,6 +53,40 @@ function eval.Proc (params, body, env)
        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,
+        -- TODO: include, import, define-syntax, define-values(?) ...
+}
+-- Aliases
+specials.lam = specials.lambda
+specials.def = specials.define
 function eval.eval (x, env)
        env = env or base.env
        if isa(x, "Symbol") then
@@ -61,23 +95,8 @@ function eval.eval (x, env)
                return x
        else
                local op, args = x.car, x.cdr
-                if op == "quote" then
+                if specials[op] then
-                        return args.car
+                        return specials[op](args, env)
-                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.eval(op, env)
                        local params = {}
author	Case Duckworth	2024-03-23 15:51:07 -0500
committer	Case Duckworth	2024-03-23 15:51:27 -0500
commit	4fb6e90474c8e9292df1a6210b8de260dd253ccb (patch)
tree	ae56acdb2d090ed36184b36635f41b692a652188
parent	Add a bunch of base functions (diff)
download	lam-4fb6e90474c8e9292df1a6210b8de260dd253ccb.tar.gz lam-4fb6e90474c8e9292df1a6210b8de260dd253ccb.zip

diff --git a/eval.lua b/eval.lua index 9b1c315..610b902 100644 --- a/eval.lua +++ b/eval.lua
@@ -53,6 +53,40 @@ function eval.Proc (params, body, env)
53	return setmetatable(v, mt)	53	return setmetatable(v, mt)
54	end	54	end
55		55
		56	local specials = {
		57	quote =
		58	function (args, env)
		59	return args.car
		60	end,
		61	define =
		62	function (args, env)
		63	rawset(env, args.car, eval(args.cdr.car, env))
		64	return nil
		65	end,
		66	lambda =
		67	function (args, env)
		68	return Proc(args.car, args.cdr, env)
		69	end,
		70	["set!"] =
		71	function (args, env)
		72	env[args.car] = eval(args.cdr.car, env)
		73	return nil
		74	end,
		75	["if"] =
		76	function (args, env)
		77	local test, conseq, alt =
		78	args.car, args.cdr.car, args.cdr.cdr.car
		79	if eval(test)
		80	then return eval(conseq)
		81	else return eval(alt)
		82	end
		83	end,
		84	-- TODO: include, import, define-syntax, define-values(?) ...
		85	}
		86	-- Aliases
		87	specials.lam = specials.lambda
		88	specials.def = specials.define
		89
56	function eval.eval (x, env)	90	function eval.eval (x, env)
57	env = env or base.env	91	env = env or base.env
58	if isa(x, "Symbol") then	92	if isa(x, "Symbol") then
@@ -61,23 +95,8 @@ function eval.eval (x, env)
61	return x	95	return x
62	else	96	else
63	local op, args = x.car, x.cdr	97	local op, args = x.car, x.cdr
64	if op == "quote" then	98	if specials[op] then
65	return args.car	99	return specials[op](args, env)
66	elseif op == "define" or op == "def" then
67	rawset(env, args.car, eval.eval(args.cdr.car, env))
68	return nil
69	elseif op == "set!" then
70	env[args.car] = eval.eval(args.cdr.car, env)
71	elseif op == "lambda" or op == "lam" then
72	return eval.Proc(args.car, args.cdr, env)
73	elseif op == "if" then
74	assert(not isNull(args.cdr), "Malformed 'if'")
75	local test, conseq, alt =
76	args.car, args.cdr.car, args.cdr.cdr.car
77	if eval.eval(test)
78	then return eval.eval(conseq)
79	else return eval.eval(alt)
80	end
81	else -- procedure	100	else -- procedure
82	local proc = eval.eval(op, env)	101	local proc = eval.eval(op, env)
83	local params = {}	102	local params = {}