tests: Add test for literal empty list in step3

[jackhill/mal.git] / process / step4_if_fn_do.txt

--- step4_if_fn_do ------------------------------
import types, reader, printer, env, core

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

eval_ast(ast,env):
  switch type(ast):
    symbol:      return env.get(ast)
    list,vector: return ast.map((x) -> EVAL(x,env))
    hash:        return ast.map((k,v) -> list(k, EVAL(v,env)))
    _default_:   return ast

EVAL(ast,env):
    if not list?(ast): return eval_ast(ast, env)
    switch ast[0]:
      'def!:        return env.set(ast[1], EVAL(ast[2], env))
      'let*:        let_env = ...; return EVAL(ast[2], let_env)
      'do:          return eval_ast(rest(ast), env)[-1]
      'if:          return EVAL(EVAL(ast[1], env) ? ast[2] : ast[3], env)
      'fn*:         return (...a) -> EVAL(ast[2], new Env(env, ast[1], a))
      _default_:    f, args = eval_ast(ast, env)
                    return apply(f, args)

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

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

;; core.EXT: defined using Racket
core.ns.map((k,v) -> (repl_env.set(k, v)))

;; core.mal: defined using the language itself
rep("(def! not (fn* (a) (if a false true)))")

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)
  find(k): return data.has(k) ? this : (if outer ? find(outer) : null)
  get(k): return data.find(k).get(k) OR raise "'" + k + "' not found"

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

      '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(" ")),

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

      'list:     list,
      'list?:    list?,

      'empty?:   empty?,
      'count:    count}