process/step7_quote.txt

   1 --- step7_quote ---------------------------------
   2 import types, reader, printer, env, core
   3
   4 READ(str): return reader.read_str(str)
   5
   6 pair?(ast): return ... // true if non-empty sequence
   7 quasiquote(ast): return ... // quasiquote
   8
   9 eval_ast(ast,env):
  10   switch type(ast):
  11     symbol:      return env.get(ast)
  12     list,vector: return ast.map((x) -> EVAL(x,env))
  13     hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
  14     _default_:   return ast
  15
  16 EVAL(ast,env):
  17   while true:
  18     if not list?(ast): return eval_ast(ast, env)
  19     if empty?(ast): return ast
  20     switch ast[0]:
  21       'def!:        return env.set(ast[1], EVAL(ast[2], env))
  22       'let*:        env = ...; ast = ast[2] // TCO
  23       'quote:       return ast[1]
  24       'quasiquote:  ast = quasiquote(ast[1]) // TCO
  25       'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
  26       'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
  27       'fn*:         return new MalFunc(...)
  28       _default_:    f, args = eval_ast(ast, env)
  29                     if malfunc?(f): ast = f.fn; env = ... // TCO
  30                     else:           return apply(f, args)
  31
  32 PRINT(exp): return printer.pr_str(exp)
  33
  34 repl_env = new Env()
  35 rep(str): return PRINT(EVAL(READ(str),repl_env))
  36
  37 ;; core.EXT: defined using Racket
  38 core.ns.map((k,v) -> (repl_env.set(k, v)))
  39 repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
  40 repl_env.set('*ARGV*, cmdline_args[1..])
  41
  42 ;; core.mal: defined using the language itself
  43 rep("(def! not (fn* (a) (if a false true)))")
  44 rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")
  45
  46 if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
  47
  48 main loop:
  49   try:      println(rep(readline("user> ")))
  50   catch e:  println("Error: ", e)
  51
  52 --- env module ----------------------------------
  53 class Env (outer=null,binds=[],exprs=[])
  54     data = hash_map()
  55     foreach b, i in binds:
  56       if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
  57       else: data[binds[i]] = exprs[i]
  58   set(k,v): return data.set(k,v)
  59   find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
  60   get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
  61
  62 --- core module ---------------------------------
  63 ns = {'=:        equal?,
  64
  65       'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
  66       'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
  67       'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
  68       'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
  69       'read-string: read_str,
  70       'slurp     read-file,
  71
  72       '<:        lt,
  73       '<=:       lte,
  74       '>:        gt,
  75       '>=:       gte,
  76       '+:        add,
  77       '-:        sub,
  78       '*:        mult,
  79       '/:        div,
  80
  81       'list:     list,
  82       'list?:    list?,
  83
  84       'cons:     (a) -> concat([a[0]], a[1]),
  85       'concat:   (a) -> reduce(concat, [], a),
  86       'empty?:   empty?,
  87       'count:    count,
  88
  89       'atom:     (a) -> new Atom(a[0]),
  90       'atom?:    (a) -> type(a[0]) == "atom",
  91       'deref:    (a) -> a[0].val,
  92       'reset!:   (a) -> a[0].val = a[1],
  93       'swap!:    swap!}