nim/step3_env.nim

   1 import rdstdin, tables, sequtils, types, reader, printer, env
   2
   3 proc read(str: string): MalType = str.read_str
   4
   5 proc eval(ast: MalType, env: var Env): MalType
   6
   7 proc eval_ast(ast: MalType, env: var Env): MalType =
   8   case ast.kind
   9   of Symbol:
  10     result = env.get(ast.str)
  11   of List:
  12     result = list ast.list.mapIt(MalType, it.eval(env))
  13   of Vector:
  14     result = vector ast.list.mapIt(MalType, it.eval(env))
  15   of HashMap:
  16     result = hash_map()
  17     for k, v in ast.hash_map.pairs:
  18       result.hash_map[k] = v.eval(env)
  19   else:
  20     result = ast
  21
  22 proc eval(ast: MalType, env: var Env): MalType =
  23   case ast.kind
  24   of List:
  25     let
  26       a0 = ast.list[0]
  27       a1 = ast.list[1]
  28       a2 = ast.list[2]
  29
  30     case a0.str
  31     of "def!":
  32       result = env.set(a1.str, a2.eval(env))
  33     of "let*":
  34       var letEnv: Env
  35       letEnv.deepCopy(env)
  36       case a1.kind
  37       of List, Vector:
  38         for i in countup(0, a1.list.high, 2):
  39           letEnv.set(a1.list[i].str, a1.list[i+1].eval(letEnv))
  40       else: discard
  41       result = a2.eval(letEnv)
  42     else:
  43       let el = ast.eval_ast(env)
  44       result = el.list[0].fun(el.list[1 .. ^1])
  45   else:
  46     result = ast.eval_ast(env)
  47
  48 proc print(exp: MalType): string = exp.pr_str
  49
  50 template wrapNumberFun(op: expr): expr =
  51   fun proc(xs: varargs[MalType]): MalType = number op(xs[0].number, xs[1].number)
  52
  53 var repl_env = initEnv()
  54
  55 repl_env.set("+", wrapNumberFun(`+`))
  56 repl_env.set("-", wrapNumberFun(`-`))
  57 repl_env.set("*", wrapNumberFun(`*`))
  58 repl_env.set("/", wrapNumberFun(`div`))
  59 #repl_env.set("/", wrapNumberFun(proc(x,y: int): int = int(x.float / y.float)))
  60
  61 proc rep(str: string): string =
  62   str.read.eval(repl_env).print
  63
  64 while true:
  65   try:
  66     let line = readLineFromStdin("user> ")
  67     echo line.rep
  68   except:
  69     echo getCurrentExceptionMsg()
  70     echo getCurrentException().getStackTrace()