io/step2_eval.io

   1 MalTypes
   2 MalReader
   3
   4 READ := method(str, MalReader read_str(str))
   5
   6 eval_ast := method(ast, env,
   7    (ast type) switch(
   8        "MalSymbol", env at(ast val) ifNil(Exception raise("'" .. (ast val) "' not found")),
   9        "MalList", MalList with(ast map(a, EVAL(a, env))),
  10        "MalVector", MalVector with(ast map(a, EVAL(a, env))),
  11        "MalMap",
  12            m := MalMap clone
  13            ast foreach(k, v,
  14                keyObj := MalMap keyToObj(k)
  15                m atPut(MalMap objToKey(EVAL(keyObj, env)), EVAL(v, env))
  16            )
  17            m,
  18        ast
  19    )
  20 )
  21
  22 EVAL := method(ast, env,
  23     if(ast type != "MalList", return(eval_ast(ast, env)))
  24     if(ast isEmpty, return ast)
  25     el := eval_ast(ast, env)
  26     f := el at(0)
  27     args := el rest
  28     f callWithArgList(args)
  29 )
  30
  31 PRINT := method(exp, exp malPrint(true))
  32
  33 repl_env := Map with(
  34     "+", block(a, b, a + b),
  35     "-", block(a, b, a - b),
  36     "*", block(a, b, a * b),
  37     "/", block(a, b, a / b)
  38 )
  39
  40 RE := method(str, EVAL(READ(str), repl_env))
  41
  42 REP := method(str, PRINT(RE(str)))
  43
  44 loop(
  45     line := MalReadline readLine("user> ")
  46     if(line isNil, break)
  47     if(line isEmpty, continue)
  48     e := try(REP(line) println)
  49     e catch(Exception,
  50         ("Error: " .. (e error)) println
  51     )
  52 )