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     if ast.list.len == 0: return ast
  26     let
  27       a0 = ast.list[0]
  28       a1 = ast.list[1]
  29       a2 = ast.list[2]
  30
  31     case a0.str
  32     of "def!":
  33       result = env.set(a1.str, a2.eval(env))
  34     of "let*":
  35       var letEnv: Env
  36       letEnv.deepCopy(env)
  37       case a1.kind
  38       of List, Vector:
  39         for i in countup(0, a1.list.high, 2):
  40           letEnv.set(a1.list[i].str, a1.list[i+1].eval(letEnv))
  41       else: discard
  42       result = a2.eval(letEnv)
  43     else:
  44       let el = ast.eval_ast(env)
  45       result = el.list[0].fun(el.list[1 .. ^1])
  46   else:
  47     result = ast.eval_ast(env)
  48
  49 proc print(exp: MalType): string = exp.pr_str
  50
  51 template wrapNumberFun(op: expr): expr =
  52   fun proc(xs: varargs[MalType]): MalType = number op(xs[0].number, xs[1].number)
  53
  54 var repl_env = initEnv()
  55
  56 repl_env.set("+", wrapNumberFun(`+`))
  57 repl_env.set("-", wrapNumberFun(`-`))
  58 repl_env.set("*", wrapNumberFun(`*`))
  59 repl_env.set("/", wrapNumberFun(`div`))
  60 #repl_env.set("/", wrapNumberFun(proc(x,y: int): int = int(x.float / y.float)))
  61
  62 proc rep(str: string): string =
  63   str.read.eval(repl_env).print
  64
  65 while true:
  66   try:
  67     let line = readLineFromStdin("user> ")
  68     echo line.rep
  69   except:
  70     echo getCurrentExceptionMsg()
  71     echo getCurrentException().getStackTrace()