basic/step1_read_print.in.bas

   1 GOTO MAIN
   2
   3 REM $INCLUDE: 'readline.in.bas'
   4 REM $INCLUDE: 'types.in.bas'
   5 REM $INCLUDE: 'reader.in.bas'
   6 REM $INCLUDE: 'printer.in.bas'
   7
   8 REM $INCLUDE: 'debug.in.bas'
   9
  10 REM READ(A$) -> R%
  11 MAL_READ:
  12   GOSUB READ_STR
  13   RETURN
  14
  15 REM EVAL(A%, E%) -> R%
  16 EVAL:
  17   R%=A%
  18   RETURN
  19
  20 REM PRINT(A%) -> R$
  21 MAL_PRINT:
  22   AZ%=A%: PR%=1: GOSUB PR_STR
  23   RETURN
  24
  25 REM REP(A$) -> R$
  26 REP:
  27   GOSUB MAL_READ
  28   IF ER%<>0 THEN GOTO REP_DONE
  29
  30   A%=R%: GOSUB EVAL
  31   IF ER%<>0 THEN GOTO REP_DONE
  32
  33   A%=R%: GOSUB MAL_PRINT
  34   RT$=R$
  35
  36   REP_DONE:
  37     REM Release memory from EVAL
  38     AY%=R%: GOSUB RELEASE
  39     R$=RT$
  40     RETURN
  41
  42 REM MAIN program
  43 MAIN:
  44   GOSUB INIT_MEMORY
  45
  46   ZT%=ZI%: REM top of memory after base repl_env
  47
  48   REPL_LOOP:
  49     A$="user> ": GOSUB READLINE: REM call input parser
  50     IF EOF=1 THEN GOTO QUIT
  51
  52     A$=R$: GOSUB REP: REM call REP
  53
  54     IF ER%<>0 THEN GOSUB PRINT_ERROR: GOTO REPL_LOOP
  55     PRINT R$
  56     GOTO REPL_LOOP
  57
  58   QUIT:
  59     REM P1%=ZT%: P2%=-1: GOSUB PR_MEMORY
  60     GOSUB PR_MEMORY_SUMMARY
  61     END
  62
  63   PRINT_ERROR:
  64     PRINT "Error: "+ER$
  65     ER%=0: ER$=""
  66     RETURN
  67