process/step6_file.txt

   1 --- step6_file ----------------------------------
   2 import types, reader, printer, env, core
   3
   4 READ(str): return reader.read_str(str)
   5
   6 eval_ast(ast,env):
   7   switch type(ast):
   8     symbol:      return env.get(ast)
   9     list,vector: return ast.map((x) -> EVAL(x,env))
  10     hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
  11     _default_:   return ast
  12
  13 EVAL(ast,env):
  14   while true:
  15     if not list?(ast): return eval_ast(ast, env)
  16     if empty?(ast): return ast
  17     switch ast[0]:
  18       'def!:        return env.set(ast[1], EVAL(ast[2], env))
  19       'let*:        env = ...; ast = ast[2] // TCO
  20       'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
  21       'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
  22       'fn*:         return new MalFunc(...)
  23       _default_:    f, args = eval_ast(ast, env)
  24                     if malfunc?(f): ast = f.fn; env = ... // TCO
  25                     else:           return apply(f, args)
  26
  27 PRINT(exp): return printer.pr_str(exp)
  28
  29 repl_env = new Env()
  30 rep(str): return PRINT(EVAL(READ(str),repl_env))
  31
  32 ;; core.EXT: defined using Racket
  33 core.ns.map((k,v) -> (repl_env.set(k, v)))
  34 repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
  35 repl_env.set('*ARGV*, cmdline_args[1..])
  36
  37 ;; core.mal: defined using the language itself
  38 rep("(def! not (fn* (a) (if a false true)))")
  39 rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \"\nnil)\")))))")
  40
  41 if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
  42
  43 main loop:
  44   try:      println(rep(readline("user> ")))
  45   catch e:  println("Error: ", e)
  46
  47 --- env module ----------------------------------
  48 class Env (outer=null,binds=[],exprs=[])
  49     data = hash_map()
  50     foreach b, i in binds:
  51       if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
  52       else: data[binds[i]] = exprs[i]
  53   set(k,v): return data.set(k,v)
  54   find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
  55   get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
  56
  57 --- core module ---------------------------------
  58 ns = {'=:        equal?,
  59
  60       'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
  61       'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
  62       'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
  63       'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
  64       'read-string: read_str,
  65       'slurp     read-file,
  66
  67       '<:        lt,
  68       '<=:       lte,
  69       '>:        gt,
  70       '>=:       gte,
  71       '+:        add,
  72       '-:        sub,
  73       '*:        mult,
  74       '/:        div,
  75
  76       'list:     list,
  77       'list?:    list?,
  78
  79       'empty?:   empty?,
  80       'count:    count,
  81
  82       'atom:     (a) -> new Atom(a[0]),
  83       'atom?:    (a) -> type(a[0]) == "atom",
  84       'deref:    (a) -> a[0].val,
  85       'reset!:   (a) -> a[0].val = a[1],
  86       'swap!:    swap!}