logo/step3_env.lg

   1 load "../logo/readline.lg
   2 load "../logo/reader.lg
   3 load "../logo/printer.lg
   4 load "../logo/types.lg
   5 load "../logo/env.lg
   6
   7 to _read :str
   8 output read_str :str
   9 end
  10
  11 to eval_ast :ast :env
  12 output case (obj_type :ast) [
  13   [[symbol]  env_get :env :ast]
  14   [[list]    obj_new "list    map [_eval ? :env] obj_val :ast]
  15   [[vector]  obj_new "vector  map [_eval ? :env] obj_val :ast]
  16   [[hashmap] obj_new "hashmap map [_eval ? :env] obj_val :ast]
  17   [else :ast]
  18 ]
  19 end
  20
  21 to _eval :ast :env
  22 if (obj_type :ast) <> "list [output eval_ast :ast :env]
  23 if emptyp obj_val :ast [output :ast]
  24 localmake "a0 nth :ast 0
  25 case list obj_type :a0 obj_val :a0 [
  26   [[[symbol def!]]
  27     localmake "a1 nth :ast 1
  28     localmake "a2 nth :ast 2
  29     output env_set :env :a1 _eval :a2 :env ]
  30
  31   [[[symbol let*]]
  32     localmake "a1 nth :ast 1
  33     localmake "letenv env_new :env [] []
  34     localmake "i 0
  35     while [:i < _count :a1] [
  36       ignore env_set :letenv nth :a1 :i _eval nth :a1 (:i + 1) :letenv
  37       make "i (:i + 2)
  38     ]
  39     output _eval nth :ast 2 :letenv ]
  40
  41   [else
  42     make "el obj_val eval_ast :ast :env
  43     output apply first :el butfirst :el ]
  44 ]
  45 end
  46
  47 to _print :exp
  48 output pr_str :exp "true
  49 end
  50
  51 to rep :str
  52 output _print _eval _read :str :repl_env
  53 end
  54
  55 to mal_add :a :b
  56 output obj_new "number ((obj_val :a) + (obj_val :b))
  57 end
  58
  59 to mal_sub :a :b
  60 output obj_new "number ((obj_val :a) - (obj_val :b))
  61 end
  62
  63 to mal_mul :a :b
  64 output obj_new "number ((obj_val :a) * (obj_val :b))
  65 end
  66
  67 to mal_div :a :b
  68 output obj_new "number ((obj_val :a) / (obj_val :b))
  69 end
  70
  71 to repl
  72 localmake "running "true
  73 while [:running] [
  74   localmake "line readline word "user> :space_char
  75   ifelse :line=[] [
  76     print "
  77     make "running "false
  78   ] [
  79     if not emptyp :line [
  80       catch "error [print rep :line]
  81       localmake "exception error
  82       if not emptyp :exception [
  83         (print "Error: first butfirst :exception)
  84       ]
  85     ]
  86   ]
  87 ]
  88 end
  89
  90 make "repl_env env_new [] [] []
  91 ignore env_set :repl_env obj_new "symbol "+ "mal_add
  92 ignore env_set :repl_env obj_new "symbol "- "mal_sub
  93 ignore env_set :repl_env obj_new "symbol "* "mal_mul
  94 ignore env_set :repl_env obj_new "symbol "/ "mal_div
  95 repl
  96 bye