amforth-devel

[Amforth-devel] Changing the word used for output and input

[Christian B. <cas...@ca...>]

Servus, (=bavarian for hello and goodbye)

I want to make a forth-based home computer. And I already got so far as to 
write accompanying video routines for it.

So I can currently enter something like emit_tv and a character will appear on 
the monitor. The hardware actually just consists of 2 resistors. :) If you 
are interested I can upload pictures of the current system somewhere.

Now my big question is, how do I redirect the output of the forth system to 
the emit_tv word?

Servus
  Casandro

Re: [Amforth-devel] Changing the word used for output and input

[Matthias T. <mt...@we...>]

Hi,

> Now my big question is, how do I redirect the output of the forth system to 
> the emit_tv word?

just do

' your-emit is emit

at the prompt or inside a colon definition

: 2tv ['] your-emit is emit ;

The IS/DEFER is based upon a forth200x standard see

http://www.forth200x.org/deferred.html for the
details.

Bye
Matthias

Re: [Amforth-devel] Changing the word used for output and input

[Christian B. <cas...@ca...>]

Am Freitag 07 März 2008 17:22:08 schrieb Matthias Trute:
> Hi,
>
> > Now my big question is, how do I redirect the output of the forth system
> > to the emit_tv word?
>
> just do
>
> ' your-emit is emit

Thanks, that works fine, but how can I change that permanently? In the next 
step of my project I will loose the serial line, but gain a keyboard, so I'd 
like to change input and output to those new devices.

> The IS/DEFER is based upon a forth200x standard see
>
> http://www.forth200x.org/deferred.html for the
> details.

Unfortunately I know far to little about Forth to understand that.

> Bye
> Matthias

Servus
  Casandro

Re: [Amforth-devel] Changing the word used for output and input

[Matthias T. <mt...@we...>]

Christian Berger wrote:
> Am Freitag 07 März 2008 17:22:08 schrieb Matthias Trute:
>> Hi,
>>
>>> Now my big question is, how do I redirect the output of the forth system
>>> to the emit_tv word?
>> just do
>>
>> ' your-emit is emit
> 
> Thanks, that works fine, but how can I change that permanently?

similiar: amforth defines a deferred word named turnkey which is
executed whever the controller starts up. The default turnkey is
defined in the application/words/turnkey.asm file and sets up the
serial line, turns the interrupts on and prints the version number.

You turnkey action may look like

--------------
: my-turnkey ( now your code goes here ) ;

' my-turnkey is turnkey
---------------

And the default turnkey action is changed to yours. Be aware that
the default turnkey action is not saved, you may need to re-flash
the eeprom (turnkey is a EEPROM based DEFER word).

>> The IS/DEFER is based upon a forth200x standard see
>>
>> http://www.forth200x.org/deferred.html for the
>> details.
> 
> Unfortunately I know far to little about Forth to understand that.

Its a elegant way to do vectored execution. Traditional forth
would express it like the first amforth versions: A variable named
'<something> and a word named <something> that reads the content of
the variable '<something> and executes the XT stored there.

------ old

variable 'something
: something 'something @ execute ;
' a-word 'someting !
something

------- new

RDEFER something
' a-word IS something
something
---------

afterwards something will execute a-word when called. The RDEFER is
used to express that the XT vector is stored in RAM. Other possibilities
are EDEFER (for EEPROM) and UDEFER (for the user area). An IDEFER would
use a flash cell. The IS is always the same, for all deferred words.

Note that the DEFER/IS words are almost lowercase and need to
be loaded from the file lib/defer.fs since the core system contains the
runtime words only ;=)

Bye
Matthias