coffee/step7_quote.coffee

   1 readline = require "./node_readline.coffee"
   2 types = require "./types.coffee"
   3 reader = require "./reader.coffee"
   4 printer = require "./printer.coffee"
   5 Env = require("./env.coffee").Env
   6 core = require("./core.coffee")
   7
   8 # read
   9 READ = (str) -> reader.read_str str
  10
  11 # eval
  12 is_pair = (x) -> types._sequential_Q(x) && x.length > 0
  13
  14 quasiquote = (ast) ->
  15   if !is_pair(ast) then [types._symbol('quote'), ast]
  16   else if ast[0] != null && ast[0].name == 'unquote' then ast[1]
  17   else if is_pair(ast[0]) && ast[0][0].name == 'splice-unquote'
  18     [types._symbol('concat'), ast[0][1], quasiquote(ast[1..])]
  19   else
  20     [types._symbol('cons'), quasiquote(ast[0]), quasiquote(ast[1..])]
  21
  22
  23
  24 eval_ast = (ast, env) ->
  25   if types._symbol_Q(ast) then env.get ast
  26   else if types._list_Q(ast) then ast.map((a) -> EVAL(a, env))
  27   else if types._vector_Q(ast)
  28     types._vector(ast.map((a) -> EVAL(a, env))...)
  29   else if types._hash_map_Q(ast)
  30     new_hm = {}
  31     new_hm[k] = EVAL(ast[k],env) for k,v of ast
  32     new_hm
  33   else ast
  34
  35 EVAL = (ast, env) ->
  36  loop
  37   #console.log "EVAL:", printer._pr_str ast
  38   if !types._list_Q ast then return eval_ast ast, env
  39   if ast.length == 0 then return ast
  40
  41   # apply list
  42   [a0, a1, a2, a3] = ast
  43   switch a0.name
  44     when "def!"
  45       return env.set(a1, EVAL(a2, env))
  46     when "let*"
  47       let_env = new Env(env)
  48       for k,i in a1 when i %% 2 == 0
  49         let_env.set(a1[i], EVAL(a1[i+1], let_env))
  50       ast = a2
  51       env = let_env
  52     when "quote"
  53       return a1
  54     when "quasiquote"
  55       ast = quasiquote(a1)
  56     when "do"
  57       eval_ast(ast[1..-2], env)
  58       ast = ast[ast.length-1]
  59     when "if"
  60       cond = EVAL(a1, env)
  61       if cond == null or cond == false
  62         if a3? then ast = a3 else return null
  63       else
  64         ast = a2
  65     when "fn*"
  66       return types._function(EVAL, a2, env, a1)
  67     else
  68       [f, args...] = eval_ast ast, env
  69       if types._function_Q(f)
  70         ast = f.__ast__
  71         env = f.__gen_env__(args)
  72       else
  73         return f(args...)
  74
  75
  76 # print
  77 PRINT = (exp) -> printer._pr_str exp, true
  78
  79 # repl
  80 repl_env = new Env()
  81 rep = (str) -> PRINT(EVAL(READ(str), repl_env))
  82
  83 # core.coffee: defined using CoffeeScript
  84 repl_env.set types._symbol(k), v for k,v of core.ns
  85 repl_env.set types._symbol('eval'), (ast) -> EVAL(ast, repl_env)
  86 repl_env.set types._symbol('*ARGV*'), []
  87
  88 # core.mal: defined using the language itself
  89 rep("(def! not (fn* (a) (if a false true)))");
  90 rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \"\nnil)\")))))");
  91
  92 if process? && process.argv.length > 2
  93   repl_env.set types._symbol('*ARGV*'), process.argv[3..]
  94   rep('(load-file "' + process.argv[2] + '")')
  95   process.exit 0
  96
  97 # repl loop
  98 while (line = readline.readline("user> ")) != null
  99   continue if line == ""
 100   try
 101     console.log rep line
 102   catch exc
 103     continue if exc instanceof reader.BlankException
 104     if exc.stack? and exc.stack.length > 2000
 105       console.log exc.stack.slice(0,1000) + "\n  ..." + exc.stack.slice(-1000)
 106     else if exc.stack? then console.log exc.stack
 107     else                    console.log exc
 108
 109 # vim: ts=2:sw=2