logo/step1_read_print.lg

   1 load "../logo/readline.lg
   2 load "../logo/reader.lg
   3 load "../logo/printer.lg
   4
   5 to _read :str
   6 output read_str :str
   7 end
   8
   9 to _eval :ast :env
  10 output :ast
  11 end
  12
  13 to _print :exp
  14 output pr_str :exp "true
  15 end
  16
  17 to rep :str
  18 output _print _eval _read :str []
  19 end
  20
  21 to repl
  22 localmake "running "true
  23 while [:running] [
  24   localmake "line readline word "user> :space_char
  25   ifelse :line=[] [
  26     print "
  27     make "running "false
  28   ] [
  29     if not emptyp :line [
  30       catch "error [print rep :line]
  31       localmake "exception error
  32       if not emptyp :exception [
  33         (print "Error: first butfirst :exception)
  34       ]
  35     ]
  36   ]
  37 ]
  38 end
  39
  40 repl
  41 bye