[Amforth] patch for amforth-shell.py

[Tristan W. <ho...@tj...>]

amforth-shell.py replaces known mcu register names with their
values. This makes it very easy to create a file like this and upload
it to the mcu (in this case avr8)

#include ms.frt

: low     ( mask port --   ) dup c@ rot invert and swap c! ;
: high    ( mask port --   ) dup c@ rot or swap c! ;

: blink ( -- )
    #32 DDRB high
    begin
        #32 PORTB low 
        1000 ms
        #32 PORTB high
        1000 ms
    key? until
;

connecting via serial and typing blink makes the led on pin 13 of an
uno blink until a key is pressed. However, the Forth system knows
nothing about DDRB or PORTB as these were substituted on-the-fly by
amforth-shell.py during the upload. This does save some flash memory
and does simplify writing code, but it is not always what you want. If
you wanted to use PORTB at the interpreter prompt, you can't as it
does not exist as a constant. Adding

#37 constant PORTB

will not help either, as amforth-shell.py still substitutes on-the-fly
creating a new word $25, as

' $25 execute .

will show. I looked to see if I could turn this behaviour off, but
I couldn't find an option to do this. The patch below changes this,
adding the option

  --no-regsub, -X       Do NOT replace mcu registers with their values.

The default behaviour remains unchanged, with register names
substituted on-the-fly.

--- ../amforth-6.93/tools/amforth-shell.py	2020-12-03 15:29:07.000000000 +0000
+++ ../amforth-6.93/tools/new-shell.py	2020-12-16 17:42:48.000000000 +0000
@@ -648,9 +648,12 @@
             help="Add Include directory")
         parser.add_argument("--uploaded-wl", "-U", action="store_true", default=False,
             help="Keep the list of uploaded filenames in the dictionary.")
+        parser.add_argument("--no-regsub", "-X", action="store_true", default=False,
+            help="Do NOT replace mcu registers with their values.")
 
         parser.add_argument("files", nargs="*", help="may be found via the environment variable AMFORTH_LIB")
         arg = parser.parse_args()
+        self.noregsub = arg.no_regsub 
         self.debug = arg.debug_serial
         self.max_line_length = arg.line_length
         self._serial_port = arg.port
@@ -917,7 +920,7 @@
                 continue
             if w in self._appl_defs:
                 w = self._appl_defs[w]
-            elif w in self._amforth_regs:
+            elif w in self._amforth_regs and not self.noregsub :
                 w = self._amforth_regs[w]
             elif w.upper() in self.stdwords:
                 w = w.lower()