From 70ec5254814f9531e5ca2024465d0e01130306b7 Mon Sep 17 00:00:00 2001
From: Case Duckworth
Date: Wed, 21 Feb 2024 09:28:49 -0600
Subject: Initial commit

---
 read.lua | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 read.lua

(limited to 'read.lua')

diff --git a/read.lua b/read.lua
new file mode 100644
index 0000000..72bbd4d
--- /dev/null
+++ b/read.lua
@@ -0,0 +1,74 @@
+--- lam.read
+
+local read = {}
+
+local types = require "types"
+local util = require "util"
+
+function read.tokenize (str)
+	--[[ Convert a string of characters into a list of tokens ]]
+	assert(str, "No program given")
+	local tbl = {}
+	local word = ""
+	local push_word =
+		function ()
+			if word:len() > 0 then
+				table.insert(tbl, word)
+				word = ""
+			end
+		end
+
+	for c = 1, #str do
+		char = string.char(str:byte(c))
+		if char == " " or char == "\t" or char == "\n" then
+			push_word()
+		elseif char == "(" then
+			push_word()
+			table.insert(tbl, "(")
+		elseif char == ")" then
+			push_word()
+			table.insert(tbl, ")")
+		else
+			word = word .. char
+		end
+	end
+	push_word()
+	return tbl
+end
+
+function read.read (str)
+	-- [[ Read a scheme expression from a string ]]
+
+	local function Atom (token)
+		local n = tonumber(token)
+		if n then return n
+		else return tostring(token)
+		end
+	end
+
+	local function read_tokens (tokens)
+		--[[ Read a list of tokens from `tokenize' ]]
+		assert(next(tokens), "Unexpected EOF")
+		token = util.pop(tokens)
+		if token == "(" then
+			local L = {}
+			while tokens[1] ~= ")" do
+				table.insert(L, read_tokens(tokens))
+			end
+			util.pop(tokens)		       --  remove ")"
+			return L
+		elseif token == ")" then
+			error("Unexpected ')'")
+		else
+			return Atom(token)
+		end
+	end
+
+	return read_tokens(read.tokenize(str))
+end
+
+return setmetatable(read, { __call =
+				    function(_, str)
+					    return read.read(str)
+				    end,
+})
-- 
cgit 1.4.1-21-gabe81