docs/steps/stepA_interop2.txt

   1 --- stepA_interop -------------------------------
   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 macro?(ast, env): return ... // true if macro function
  10 macroexpand(ast, env): return ... // recursive macro expansion
  11
  12 eval_ast(ast,env):
  13   switch type(ast):
  14     symbol:      return env.get(ast)
  15     list,vector: return ast.map((x) -> EVAL(x,env))
  16     hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
  17     _default_:   return ast
  18
  19 EVAL(ast,env):
  20   while true:
  21     if not list?(ast): return eval_ast(ast, env)
  22     switch ast[0]:
  23       'def!:        return env.set(ast[1], EVAL(ast[2], env))
  24       'let*:        env = ...; ast = ast[2] // TCO
  25       'quote:       return ast[1]
  26       'quasiquote:  ast = quasiquote(ast[1]) // TCO
  27       'defmacro!:   return ... // like def!, but set macro property
  28       'macroexpand: return macroexpand(ast[1], env)
  29       'try*:        return ... // try/catch native and malval exceptions
  30       'do:          ast = eval_ast(ast[1..-1], env)[-1] // TCO
  31       'if:          EVAL(ast[1], env) ? ast = ast[2] : ast = ast[3] // TCO
  32       'fn*:         return new MalFunc(...)
  33       _default_:    f, args = eval_ast(ast, env)
  34                     if malfunc?(ast[0]): ast = ast[0].fn; env = ... // TCO
  35                     else:                return apply(f, args)
  36
  37 PRINT(exp): return printer.pr_str(exp)
  38
  39 repl_env = new Env()
  40 rep(str): return PRINT(EVAL(READ(str),repl_env))
  41
  42 ;; core.EXT: defined using Racket
  43 core.ns.map((k,v) -> (repl_env.set(k, v)))
  44 repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
  45 repl_env.set('*ARGV*, cmdline_args[1..])
  46
  47 ;; core.mal: defined using the language itself
  48 rep("(def! *host-language* \"racket\")")
  49 rep("(def! not (fn* (a) (if a false true)))")
  50 rep("(def! load-file (fn* (f) ...))")
  51 rep("(defmacro! cond (fn* (& xs) ...))")
  52 rep("(defmacro! or (fn* (& xs) ...))")
  53
  54 if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0
  55
  56 rep("(println (str \"Mal [\" *host-language* \"]\"))")
  57 main loop:
  58   try:      println(rep(readline("user> ")))
  59   catch e:  println("Error: ", e)
  60
  61 --- env module ----------------------------------
  62 class Env (outer=null,binds=[],exprs=[])
  63     data = hash_map()
  64     foreach b, i in binds:
  65       if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
  66       else: data[binds[i]] = exprs[i]
  67   set(k,v): return data.set(k,v)
  68   find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
  69   get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"
  70
  71 --- core module ---------------------------------
  72 ns = {'=:        equal?,
  73       'throw:    throw,
  74
  75       'nil?:     nil?,
  76       'true?:    true?,
  77       'false?:   false?,
  78       'symbol:   symbol,
  79       'symbol?:  symbol?,
  80       'keyword:  keyword,
  81       'keyword?: keyword?,
  82
  83       'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
  84       'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
  85       'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
  86       'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
  87       'read-string: read_str,
  88       'readline: readline,
  89       'slurp     read-file,
  90
  91       '<:        lt,
  92       '<=:       lte,
  93       '>:        gt,
  94       '>=:       gte,
  95       '+:        add,
  96       '-:        sub,
  97       '*:        mult,
  98       '/:        div,
  99
 100       'list:     list,
 101       'list?:    list?,
 102       'vector:   vector,
 103       'vector?:  vector?,
 104       'hash-map: hash_map,
 105       'map?:     hash_map?,
 106       'assoc:    assoc,
 107       'dissoc:   dissoc,
 108       'get:      get,
 109       'contains?: contains?,
 110       'keys:     keys,
 111       'vals:     vals,
 112
 113       'sequential? sequential?,
 114       'cons:     (a) -> concat([a[0]], a[1]),
 115       'concat:   (a) -> reduce(concat, [], a),
 116       'nth:      (a) -> a[0][a[1]] OR raise "nth: index out of range",
 117       'first:    (a) -> a[0][0] OR nil,
 118       'rest:     (a) -> a[0][1..] OR list(),
 119       'empty?:   empty?,
 120       'count:    count,
 121       'apply:    apply,
 122       'map:      map,
 123       'conj:     conj,
 124
 125       'meta:     (a) -> a[0].meta,
 126       'with-meta: (a) -> a[0].with_meta(a[1]),
 127       'atom:     (a) -> new Atom(a[0]),
 128       'atom?:    (a) -> type(a[0]) == "atom",
 129       'deref:    (a) -> a[0].val,
 130       'reset!:   (a) -> a[0].val = a[1],
 131       'swap!:    swap!}