Lua: all steps and self-hosting.

Also some misc docs/TODO updates.

1 files changed, 127 insertions, 0 deletions

diff --git a/lua/reader.lua b/lua/reader.lua
new file mode 100644
index 0000000..2d29a52
--- /dev/null
+++ b/lua/reader.lua
@@ -0,0 +1,127 @@
+local rex = require('rex_pcre')
+local string = require('string')
+local table = require('table')
+local types = require('types')
+local throw, Nil, Symbol, List = types.throw, types.Nil,
+                                 types.Symbol, types.List
+
+local M = {}
+
+Reader = {}
+function Reader:new(tokens)
+    local newObj = {tokens = tokens, position = 1}
+    self.__index = self
+    return setmetatable(newObj, self)
+end
+function Reader:next()
+    self.position = self.position + 1
+    return self.tokens[self.position-1]
+end
+function Reader:peek()
+    return self.tokens[self.position]
+end
+
+function M.tokenize(str)
+    local results = {}
+    local re_pos = 1
+    local re = rex.new("[\\s,]*(~@|[\\[\\]{}()'`~^@]|\"(?:\\\\.|[^\\\\\"])*\"|;[^\n]*|[^\\s\\[\\]{}('\"`,;)]*)", rex.flags().EXTENDED)
+    while true do
+        local s, e, t = re:exec(str, re_pos)
+        if not s or s > e then break end
+        re_pos = e + 1
+        local val = string.sub(str,t[1],t[2])
+        if string.sub(val,1,1) ~= ";" then
+            table.insert(results, val)
+        end
+    end
+    return results
+end
+
+function M.read_atom(rdr)
+    local int_re = rex.new("^-?[0-9]+$")
+    local float_re = rex.new("^-?[0-9][0-9.]*$")
+    local token = rdr:next()
+    if int_re:exec(token) then       return tonumber(token)
+    elseif float_re:exec(token) then return tonumber(token)
+    elseif string.sub(token,1,1) == '"' then
+        local sval = string.sub(token,2,string.len(token)-1)
+        sval = string.gsub(sval, '\\"', '"')
+        sval = string.gsub(sval, '\\n', '\n')
+        return sval
+    elseif string.sub(token,1,1) == ':' then
+        return "\177" .. string.sub(token,2)
+    elseif token == "nil" then       return Nil
+    elseif token == "true" then      return true
+    elseif token == "false" then     return false
+    else                             return Symbol:new(token)
+    end
+end
+
+function M.read_sequence(rdr, start, last)
+    local ast = {}
+    local token = rdr:next()
+    if token ~= start then throw("expected '"..start.."'") end
+
+    token = rdr:peek()
+    while token ~= last do
+        if not token then throw("expected '"..last.."', got EOF") end
+        table.insert(ast, M.read_form(rdr))
+        token = rdr:peek()
+    end
+    rdr:next()
+    return ast
+end
+
+function M.read_list(rdr)
+    return types.List:new(M.read_sequence(rdr, '(', ')'))
+end
+
+function M.read_vector(rdr)
+    return types.Vector:new(M.read_sequence(rdr, '[', ']'))
+end
+
+function M.read_hash_map(rdr)
+    local seq = M.read_sequence(rdr, '{', '}')
+    return types._assoc_BANG(types.HashMap:new(), unpack(seq))
+end
+
+function M.read_form(rdr)
+    local token = rdr:peek()
+
+    if "'" == token then
+        rdr:next()
+        return List:new({Symbol:new('quote'), M.read_form(rdr)})
+    elseif '`' == token then
+        rdr:next()
+        return List:new({Symbol:new('quasiquote'), M.read_form(rdr)})
+    elseif '~' == token then
+        rdr:next()
+        return List:new({Symbol:new('unquote'), M.read_form(rdr)})
+    elseif '~@' == token then
+        rdr:next()
+        return List:new({Symbol:new('splice-unquote'), M.read_form(rdr)})
+    elseif '^' == token then
+        rdr:next()
+        local meta = M.read_form(rdr)
+        return List:new({Symbol:new('with-meta'), M.read_form(rdr), meta})
+    elseif '@' == token then
+        rdr:next()
+        return List:new({Symbol:new('deref'), M.read_form(rdr)})
+
+    elseif ')' == token then throw("unexpected ')'")
+    elseif '(' == token then return M.read_list(rdr)
+    elseif ']' == token then throw("unexpected ']'")
+    elseif '[' == token then return M.read_vector(rdr)
+    elseif '}' == token then throw("unexpected '}'")
+    elseif '{' == token then return M.read_hash_map(rdr)
+    else return M.read_atom(rdr)
+    end
+end
+
+function M.read_str(str)
+    local tokens = M.tokenize(str)
+    if #tokens == 0 then error(nil) end
+    return M.read_form(Reader:new(tokens))
+end
+
+return M