coffee/step9_try.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 is_macro_call = (ast, env) ->
  23   return types._list_Q(ast) && types._symbol_Q(ast[0]) &&
  24          env.find(ast[0]) && env.get(ast[0]).__ismacro__
  25
  26 macroexpand = (ast, env) ->
  27   while is_macro_call(ast, env)
  28     ast = env.get(ast[0])(ast[1..]...)
  29   ast
  30
  31
  32
  33 eval_ast = (ast, env) ->
  34   if types._symbol_Q(ast) then env.get ast
  35   else if types._list_Q(ast) then ast.map((a) -> EVAL(a, env))
  36   else if types._vector_Q(ast)
  37     types._vector(ast.map((a) -> EVAL(a, env))...)
  38   else if types._hash_map_Q(ast)
  39     new_hm = {}
  40     new_hm[k] = EVAL(ast[k],env) for k,v of ast
  41     new_hm
  42   else ast
  43
  44 EVAL = (ast, env) ->
  45  loop
  46   #console.log "EVAL:", printer._pr_str ast
  47   if !types._list_Q ast then return eval_ast ast, env
  48
  49   # apply list
  50   ast = macroexpand ast, env
  51   if !types._list_Q ast then return eval_ast ast, env
  52   if ast.length == 0 then return ast
  53
  54   [a0, a1, a2, a3] = ast
  55   switch a0.name
  56     when "def!"
  57       return env.set(a1, EVAL(a2, env))
  58     when "let*"
  59       let_env = new Env(env)
  60       for k,i in a1 when i %% 2 == 0
  61         let_env.set(a1[i], EVAL(a1[i+1], let_env))
  62       ast = a2
  63       env = let_env
  64     when "quote"
  65       return a1
  66     when "quasiquote"
  67       ast = quasiquote(a1)
  68     when "defmacro!"
  69       f = EVAL(a2, env)
  70       f.__ismacro__ = true
  71       return env.set(a1, f)
  72     when "macroexpand"
  73       return macroexpand(a1, env)
  74     when "try*"
  75       try return EVAL(a1, env)
  76       catch exc
  77         if a2 && a2[0].name == "catch*"
  78           if exc.object? then exc = exc.object
  79           else exc = exc.message
  80           return EVAL a2[2], new Env(env, [a2[1]], [exc])
  81         else
  82           throw exc
  83     when "do"
  84       eval_ast(ast[1..-2], env)
  85       ast = ast[ast.length-1]
  86     when "if"
  87       cond = EVAL(a1, env)
  88       if cond == null or cond == false
  89         if a3? then ast = a3 else return null
  90       else
  91         ast = a2
  92     when "fn*"
  93       return types._function(EVAL, a2, env, a1)
  94     else
  95       [f, args...] = eval_ast ast, env
  96       if types._function_Q(f)
  97         ast = f.__ast__
  98         env = f.__gen_env__(args)
  99       else
 100         return f(args...)
 101
 102
 103 # print
 104 PRINT = (exp) -> printer._pr_str exp, true
 105
 106 # repl
 107 repl_env = new Env()
 108 rep = (str) -> PRINT(EVAL(READ(str), repl_env))
 109
 110 # core.coffee: defined using CoffeeScript
 111 repl_env.set types._symbol(k), v for k,v of core.ns
 112 repl_env.set types._symbol('eval'), (ast) -> EVAL(ast, repl_env)
 113 repl_env.set types._symbol('*ARGV*'), []
 114
 115 # core.mal: defined using the language itself
 116 rep("(def! not (fn* (a) (if a false true)))");
 117 rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \"\nnil)\")))))");
 118 rep("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))")
 119
 120 if process? && process.argv.length > 2
 121   repl_env.set types._symbol('*ARGV*'), process.argv[3..]
 122   rep('(load-file "' + process.argv[2] + '")')
 123   process.exit 0
 124
 125 # repl loop
 126 while (line = readline.readline("user> ")) != null
 127   continue if line == ""
 128   try
 129     console.log rep line
 130   catch exc
 131     continue if exc instanceof reader.BlankException
 132     if exc.stack? and exc.stack.length > 2000
 133       console.log exc.stack.slice(0,1000) + "\n  ..." + exc.stack.slice(-1000)
 134     else if exc.stack?
 135       console.log exc.stack
 136     else if exc.object?
 137       console.log "Error:", printer._pr_str exc.object, true
 138     else
 139       console.log exc
 140
 141 # vim: ts=2:sw=2