From 2ae1efbc5fe2a8fd2fb967421db7bcef969428dd Mon Sep 17 00:00:00 2001
From: Case Duckworth
Date: Mon, 11 Mar 2024 00:40:31 -0500
Subject: Add QUOTE, QUASIQUOTE, UNQUOTE reading and generalize

---
 read.lua | 73 ++++++++++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 48 insertions(+), 25 deletions(-)

(limited to 'read.lua')

diff --git a/read.lua b/read.lua
index bba4ffa..c5dacc0 100644
--- a/read.lua
+++ b/read.lua
@@ -4,6 +4,7 @@ local read = {}
 local type = require "type"
 local utf8 = require "utf8"
 local util = require "util"
+local pop = util.pop
 local unpack = table.unpack or unpack
 
 function program_characters (program)
@@ -18,14 +19,14 @@ local function consume_string_whitespace (chars)
 	-- \<intraline ws>*<line ending> <intraline ws>* : nothing
 	local s = {"\\"}
 	while chars[1]:match("[ \t]") do
-		table.insert(s, util.pop(chars))
+		table.insert(s, pop(chars))
 	end
 	if chars[1] ~= "\n" then
 		table.insert(s, chars[1])
 		return table.concat(s), chars
 	end
 	while chars[1]:match("%s") do
-		util.pop(chars)
+		pop(chars)
 	end
 	return chars[1], chars
 end
@@ -34,7 +35,7 @@ local function consume_string_hexvalue (chars)
 	-- \x<hex scalar value>; : specified character
 	local u8ch = {}
 	repeat
-		local c = util.pop(chars)
+		local c = pop(chars)
 		table.insert(u8ch, c)
 	until c == ";"
 	table.remove(u8ch) -- remove semicolon
@@ -57,9 +58,9 @@ local function consume_string (chars)
 		["\n"] = consume_string_whitespace,
 		x = consume_string_hexvalue,
 	}
-	util.pop(chars) -- throw initial " away
+	pop(chars) -- throw initial " away
 	repeat
-		local c = util.pop(chars)
+		local c = pop(chars)
 		if c == [[\]] then
 			c = chars[1]
 			if backlash[c] then
@@ -72,7 +73,7 @@ local function consume_string (chars)
 			else
 				table.insert(str, "\\"..c)
 			end
-			util.pop(chars)
+			pop(chars)
 		elseif c == [["]] then
 			break
 		else
@@ -84,8 +85,8 @@ end
 
 local function consume_token (chars)
 	local tok = {}
-	while chars[1]:match("[^%s()\"#'`,@;]") do
-		table.insert(tok, util.pop(chars))
+	while #chars>0 and chars[1]:match("[^%s()\"#'`,@;]") do
+		table.insert(tok, pop(chars))
 	end
 	return table.concat(tok), chars
 end
@@ -100,14 +101,14 @@ local function consume_number (chars)
 end
 
 local function consume_whitespace (chars)
-	while chars[1]:match("%s") do util.pop(chars) end
+	while #chars>0 and chars[1]:match("%s") do pop(chars) end
 	return chars
 end
 
 local function consume_comment (chars)
 	local comment = {}
 	repeat
-		table.insert(comment, util.pop(chars))
+		table.insert(comment, pop(chars))
 	until #chars == 0 or chars[1]:match("\n")
 	return table.concat(comment), "comment", chars
 end
@@ -115,14 +116,14 @@ end
 --- API
 
 read.readtable = {
-	["("] = function(chars) return util.pop(chars), "begin_list", chars end,
-	[")"] = function(chars) return util.pop(chars), "end_list", chars end,
+	["("] = function(chars) return pop(chars), "open", chars end,
+	[")"] = function(chars) return pop(chars), "close", chars end,
+	["'"] = function(chars) return pop(chars), "quote", chars end,
+	["`"] = function(chars) return pop(chars), "quote", chars end,
+	[","] = function(chars) return pop(chars), "quote", chars end,
 	["\""] = consume_string,
 	[";"] = consume_comment,
 	-- ["#"] =
-	-- ["'"] =
-	-- ["`"] =
-	-- [","] =
 }
 
 function read.scan (chars)
@@ -157,18 +158,40 @@ function read.tokenize (program)
 	return tokens
 end
 
+read.readmacros = {
+	open =
+		function (token, tokens)
+			local L = {}
+			while tokens[1].type ~= "close" do
+				table.insert(L, read.parse(tokens))
+			end
+			pop(tokens) -- remove final ")"
+			return type.List(L)
+		end,
+	close =
+		function (token, tokens)
+			error ("Unexpected '" .. token.value .. "'")
+		end,
+	quote =
+		function (token, tokens)
+			local Q
+			if token.value == "'" then
+				Q = {"quote"}
+			elseif token.value == "`" then
+				Q = {"quasiquote"}
+			elseif token.value == "," then
+				Q = {"unquote"}
+			end
+			table.insert(Q, read.parse(tokens))
+			return type.List(Q)
+		end,
+}
+
 function read.parse (tokens)
 	if not next(tokens) then return nil end
-	local token = util.pop(tokens)
-	if token.value == "(" then
-		local L = {}
-		while tokens[1].value ~= ")" do
-			table.insert(L, read.parse(tokens))
-		end
-		util.pop(tokens) -- remove the final ")"
-		return type.List(L)
-	elseif token.value == ")" then
-		error("Unexpected ')'")
+	local token = pop(tokens)
+	if read.readmacros[token.type] then
+		return read.readmacros[token.type](token, tokens)
 	else
 		return token.value
 	end
-- 
cgit 1.4.1-21-gabe81