lua/step7_quote.lua

   1 #!/usr/bin/env lua
   2
   3 local table = require('table')
   4
   5 local readline = require('readline')
   6 local utils = require('utils')
   7 local types = require('types')
   8 local reader = require('reader')
   9 local printer = require('printer')
  10 local Env = require('env')
  11 local core = require('core')
  12 local List, Vector, HashMap = types.List, types.Vector, types.HashMap
  13
  14 -- read
  15 function READ(str)
  16     return reader.read_str(str)
  17 end
  18
  19 -- eval
  20 function is_pair(x)
  21     return types._sequential_Q(x) and #x > 0
  22 end
  23
  24 function quasiquote(ast)
  25     if not is_pair(ast) then
  26         return types.List:new({types.Symbol:new("quote"), ast})
  27     elseif types._symbol_Q(ast[1]) and ast[1].val == 'unquote' then
  28         return ast[2]
  29     elseif is_pair(ast[1]) and
  30            types._symbol_Q(ast[1][1]) and
  31            ast[1][1].val == 'splice-unquote' then
  32         return types.List:new({types.Symbol:new("concat"),
  33                                ast[1][2],
  34                                quasiquote(ast:slice(2))})
  35     else
  36         return types.List:new({types.Symbol:new("cons"),
  37                                quasiquote(ast[1]),
  38                                quasiquote(ast:slice(2))})
  39     end
  40 end
  41
  42 function eval_ast(ast, env)
  43     if types._symbol_Q(ast) then
  44         return env:get(ast)
  45     elseif types._list_Q(ast) then
  46         return List:new(utils.map(function(x) return EVAL(x,env) end,ast))
  47     elseif types._vector_Q(ast) then
  48         return Vector:new(utils.map(function(x) return EVAL(x,env) end,ast))
  49     elseif types._hash_map_Q(ast) then
  50         local new_hm = {}
  51         for k,v in pairs(ast) do
  52             new_hm[EVAL(k, env)] = EVAL(v, env)
  53         end
  54         return HashMap:new(new_hm)
  55     else
  56         return ast
  57     end
  58 end
  59
  60 function EVAL(ast, env)
  61   while true do
  62     --print("EVAL: "..printer._pr_str(ast,true))
  63     if not types._list_Q(ast) then return eval_ast(ast, env) end
  64
  65     local a0,a1,a2,a3 = ast[1], ast[2],ast[3],ast[4]
  66     local a0sym = types._symbol_Q(a0) and a0.val or ""
  67     if 'def!' == a0sym then
  68         return env:set(a1, EVAL(a2, env))
  69     elseif 'let*' == a0sym then
  70         local let_env = Env:new(env)
  71         for i = 1,#a1,2 do
  72             let_env:set(a1[i], EVAL(a1[i+1], let_env))
  73         end
  74         env = let_env
  75         ast = a2 -- TCO
  76     elseif 'quote' == a0sym then
  77         return a1
  78     elseif 'quasiquote' == a0sym then
  79         ast = quasiquote(a1) -- TCO
  80     elseif 'do' == a0sym then
  81         local el = eval_ast(ast:slice(2,#ast-1), env)
  82         ast = ast[#ast]  -- TCO
  83     elseif 'if' == a0sym then
  84         local cond = EVAL(a1, env)
  85         if cond == types.Nil or cond == false then
  86             if a3 then ast = a3 else return types.Nil end -- TCO
  87         else
  88             ast = a2 -- TCO
  89         end
  90     elseif 'fn*' == a0sym then
  91         return types.MalFunc:new(function(...)
  92             return EVAL(a2, Env:new(env, a1, arg))
  93         end, a2, env, a1)
  94     else
  95         local args = eval_ast(ast, env)
  96         local f = table.remove(args, 1)
  97         if types._malfunc_Q(f) then
  98             ast = f.ast
  99             env = Env:new(f.env, f.params, args) -- TCO
 100         else
 101             return f(unpack(args))
 102         end
 103     end
 104   end
 105 end
 106
 107 -- print
 108 function PRINT(exp)
 109     return printer._pr_str(exp, true)
 110 end
 111
 112 -- repl
 113 local repl_env = Env:new()
 114 function rep(str)
 115     return PRINT(EVAL(READ(str),repl_env))
 116 end
 117
 118 -- core.lua: defined using Lua
 119 for k,v in pairs(core.ns) do
 120     repl_env:set(types.Symbol:new(k), v)
 121 end
 122 repl_env:set(types.Symbol:new('eval'),
 123              function(ast) return EVAL(ast, repl_env) end)
 124 repl_env:set(types.Symbol:new('*ARGV*'), types.List:new(types.slice(arg,2)))
 125
 126 -- core.mal: defined using mal
 127 rep("(def! not (fn* (a) (if a false true)))")
 128 rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")
 129
 130 if #arg > 0 and arg[1] == "--raw" then
 131     readline.raw = true
 132     table.remove(arg,1)
 133 end
 134
 135 if #arg > 0 then
 136     rep("(load-file \""..arg[1].."\")")
 137     os.exit(0)
 138 end
 139
 140 while true do
 141     line = readline.readline("user> ")
 142     if not line then break end
 143     xpcall(function()
 144         print(rep(line))
 145     end, function(exc)
 146         if exc then
 147             if types._malexception_Q(exc) then
 148                 exc = printer._pr_str(exc.val, true)
 149             end
 150             print("Error: " .. exc)
 151             print(debug.traceback())
 152         end
 153     end)
 154 end