mal/process/step9_try.txt

--- step9_try -----------------------------------
import types, reader, printer, env, core

READ(str): return reader.read_str(str)

quasiquote(ast): return ... // quasiquote

EVAL(ast, env):
 loop:
  if env.get('DEBUG-EVAL) exists and not in nil, false then prn('EVAL ast)
  match ast:
    'key:                     return env.get(key) or raise "'{key}' not found"
    [form1 ..]:               return [EVAL(form1, env) ..]
    {key1 value1 ..}:         return {key1 EVAL(value1, env) ..}
    ('def! 'key value):       return env.set(key, EVAL(value, env))
    ('let* (k1 v1 ..) form):  env = new Env(env)
                              env.set(k1, EVAL(v1, env))
                              ..
                              ast = form; continue
    ('let* [k1 v1 ..] form):  // idem
    ('do form1 .. last):      EVAL(form1, env)
                              ..
                              ast = last; continue
    ('if cond yes no):        if EVAL(cond, env) in nil, false
                                then ast = yes; continue
                                else ast = no;  continue
    ('if cond yes):           // idem with return nil in the else branch
    ('fn* ('key1 ..) impl):   return new MalFn(env, impl, parm=[key1 ..])
    ('fn* ['key1 ..] impl):   // idem
    ('quote form):            return form
    ('quasiquote form):       ast = quasiquote(form); continue
    ('defmacro! 'key value):  return env.set(key, as_macro(EVAL(value, env)))
    ('try* f ('catch* 'k h)): try returning EVAL(f, env)
                              if native or malval exception then:
                                env = new Env(env)
                                env.set(k, exception)
                                ast = h; continue
    ('try* form):             ast = form; continue
    (callable arg1 ..):       f = EVAL(callable, env)
                              if macro?(f) then:
                                ast = f(arg1, ..); continue
                              args = [EVAL(arg1, env) ..]
                              if malfn?(f) then:
                                env = new Env(f.env, f.parm, args)
                                ast = f.impl; continue
                              return f(args)
    otherwise:                return ast

PRINT(exp): return printer.pr_str(exp)

repl_env = new Env()
rep(str): return PRINT(EVAL(READ(str),repl_env))

;; core.EXT: defined using the host language.
core.ns.map((k,v) -> (repl_env.set(k, v)))
repl_env.set('eval, (ast) -> EVAL(ast, repl-env))
repl_env.set('*ARGV*, cmdline_args[1..])

;; core.mal: defined using the language itself
rep("(def! not (fn* (a) (if a false true)))")
rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \"\nnil)\")))))")
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)))))))");

if cmdline_args: rep("(load-file \"" + args[0] + "\")"); exit 0

main loop:
  try:      println(rep(readline("user> ")))
  catch e:  println("Error: ", e)

--- env module ----------------------------------
class Env (outer=null,binds=[],exprs=[])
    data = hash_map()
    foreach b, i in binds:
      if binds[i] == '&: data[binds[i+1]] = exprs.drop(i); break
      else: data[binds[i]] = exprs[i]
  set(k,v): return data.set(k,v)
  get(k): return data.has(k) ? data.get(k) : (outer ? outer.get(k) : null)

--- core module ---------------------------------
ns = {'=:        equal?,
      'throw:    throw,

      'nil?:     nil?,
      'true?:    true?,
      'false?:   false?,
      'symbol:   symbol,
      'symbol?:  symbol?,
      'keyword:  keyword,
      'keyword?: keyword?,

      'pr-str:   (a) -> a.map(|s| pr_str(e,true)).join(" ")),
      'str:      (a) -> a.map(|s| pr_str(e,false)).join("")),
      'prn:      (a) -> println(a.map(|s| pr_str(e,true)).join(" ")),
      'println:  (a) -> println(a.map(|s| pr_str(e,false)).join(" ")),
      'read-string: read_str,
      'slurp     read-file,

      '<:        lt,
      '<=:       lte,
      '>:        gt,
      '>=:       gte,
      '+:        add,
      '-:        sub,
      '*:        mult,
      '/:        div,

      'list:     list,
      'list?:    list?,
      'vector:   vector,
      'vector?:  vector?,
      'hash-map: hash_map,
      'map?:     hash_map?,
      'assoc:    assoc,
      'dissoc:   dissoc,
      'get:      get,
      'contains?: contains?,
      'keys:     keys,
      'vals:     vals,

      'sequential? sequential?,
      'cons:     (a) -> concat([a[0]], a[1]),
      'concat:   (a) -> reduce(concat, [], a),
      'vec:      (l) -> l converted to vector,
      'nth:      (a) -> a[0][a[1]] OR raise "nth: index out of range",
      'first:    (a) -> a[0][0] OR nil,
      'rest:     (a) -> a[0][1..] OR list(),
      'empty?:   empty?,
      'count:    count,
      'apply:    apply,
      'map:      map,

      'atom:     (a) -> new Atom(a[0]),
      'atom?:    (a) -> type(a[0]) == "atom",
      'deref:    (a) -> a[0].val,
      'reset!:   (a) -> a[0].val = a[1],
      'swap!:    swap!}