lua/reader.lua

   1 local rex = require('rex_pcre')
   2 local string = require('string')
   3 local table = require('table')
   4 local types = require('types')
   5 local throw, Nil, Symbol, List = types.throw, types.Nil,
   6                                  types.Symbol, types.List
   7
   8 local M = {}
   9
  10 Reader = {}
  11 function Reader:new(tokens)
  12     local newObj = {tokens = tokens, position = 1}
  13     self.__index = self
  14     return setmetatable(newObj, self)
  15 end
  16 function Reader:next()
  17     self.position = self.position + 1
  18     return self.tokens[self.position-1]
  19 end
  20 function Reader:peek()
  21     return self.tokens[self.position]
  22 end
  23
  24 function M.tokenize(str)
  25     local results = {}
  26     local re_pos = 1
  27     local re = rex.new("[\\s,]*(~@|[\\[\\]{}()'`~^@]|\"(?:\\\\.|[^\\\\\"])*\"?|;[^\n]*|[^\\s\\[\\]{}('\"`,;)]*)", rex.flags().EXTENDED)
  28     while true do
  29         local s, e, t = re:exec(str, re_pos)
  30         if not s or s > e then break end
  31         re_pos = e + 1
  32         local val = string.sub(str,t[1],t[2])
  33         if string.sub(val,1,1) ~= ";" then
  34             table.insert(results, val)
  35         end
  36     end
  37     return results
  38 end
  39
  40 function M.read_atom(rdr)
  41     local int_re = rex.new("^-?[0-9]+$")
  42     local float_re = rex.new("^-?[0-9][0-9.]*$")
  43     local string_re = rex.new("^\"(?:\\\\.|[^\\\\\"])*\"$")
  44     local token = rdr:next()
  45     if int_re:exec(token) then       return tonumber(token)
  46     elseif float_re:exec(token) then return tonumber(token)
  47     elseif string_re:exec(token) then
  48         local sval = string.sub(token,2,string.len(token)-1)
  49         sval = string.gsub(sval, '\\\\', '\177')
  50         sval = string.gsub(sval, '\\"', '"')
  51         sval = string.gsub(sval, '\\n', '\n')
  52         sval = string.gsub(sval, '\177', '\\')
  53         return sval
  54     elseif string.sub(token,1,1) == '"' then
  55         throw("expected '\"', got EOF")
  56     elseif string.sub(token,1,1) == ':' then
  57         return "\177" .. string.sub(token,2)
  58     elseif token == "nil" then       return Nil
  59     elseif token == "true" then      return true
  60     elseif token == "false" then     return false
  61     else                             return Symbol:new(token)
  62     end
  63 end
  64
  65 function M.read_sequence(rdr, start, last)
  66     local ast = {}
  67     local token = rdr:next()
  68     if token ~= start then throw("expected '"..start.."'") end
  69
  70     token = rdr:peek()
  71     while token ~= last do
  72         if not token then throw("expected '"..last.."', got EOF") end
  73         table.insert(ast, M.read_form(rdr))
  74         token = rdr:peek()
  75     end
  76     rdr:next()
  77     return ast
  78 end
  79
  80 function M.read_list(rdr)
  81     return types.List:new(M.read_sequence(rdr, '(', ')'))
  82 end
  83
  84 function M.read_vector(rdr)
  85     return types.Vector:new(M.read_sequence(rdr, '[', ']'))
  86 end
  87
  88 function M.read_hash_map(rdr)
  89     local seq = M.read_sequence(rdr, '{', '}')
  90     return types._assoc_BANG(types.HashMap:new(), table.unpack(seq))
  91 end
  92
  93 function M.read_form(rdr)
  94     local token = rdr:peek()
  95
  96     if "'" == token then
  97         rdr:next()
  98         return List:new({Symbol:new('quote'), M.read_form(rdr)})
  99     elseif '`' == token then
 100         rdr:next()
 101         return List:new({Symbol:new('quasiquote'), M.read_form(rdr)})
 102     elseif '~' == token then
 103         rdr:next()
 104         return List:new({Symbol:new('unquote'), M.read_form(rdr)})
 105     elseif '~@' == token then
 106         rdr:next()
 107         return List:new({Symbol:new('splice-unquote'), M.read_form(rdr)})
 108     elseif '^' == token then
 109         rdr:next()
 110         local meta = M.read_form(rdr)
 111         return List:new({Symbol:new('with-meta'), M.read_form(rdr), meta})
 112     elseif '@' == token then
 113         rdr:next()
 114         return List:new({Symbol:new('deref'), M.read_form(rdr)})
 115
 116     elseif ')' == token then throw("unexpected ')'")
 117     elseif '(' == token then return M.read_list(rdr)
 118     elseif ']' == token then throw("unexpected ']'")
 119     elseif '[' == token then return M.read_vector(rdr)
 120     elseif '}' == token then throw("unexpected '}'")
 121     elseif '{' == token then return M.read_hash_map(rdr)
 122     else return M.read_atom(rdr)
 123     end
 124 end
 125
 126 function M.read_str(str)
 127     local tokens = M.tokenize(str)
 128     if #tokens == 0 then error(nil) end
 129     return M.read_form(Reader:new(tokens))
 130 end
 131
 132 return M