I would like to define "TO" to copy a value from a memory address to a variable. I believe the default is

fromADDR TO toADDR

instead of

fromADDR toADDR TO


If the first example is correct, by the same analogy one can get a string after a word command using "BL WORD" or "QUOTE WORD"

Is there a way to get the address of "toADDR" after the word command "TO"?

Currently my definition of "TO" is (but only works for the second example)

: TO SWAP @ SWAP ! ;

This depends a lot on how you variables are implemented in your forth.
I would use ' (the single quote - sometimes called "tick") to get the XT (execution token) of the variable. It reads the next name at the input (which is what I believe you are trying to figure out how to do), looks it up, and puts that word's XT on the stack. If you use ' in a new word's definition, it will do this action when the new word is run.

Note that the XT isn't the address of the DATA in the variable, but rather is the address of the ROUTINE to run when the variable name is used. This routine normally puts the address of the data on the stack.

In TaliForth2, the routine is just a JSR (3 bytes long - Tali2 is an STC forth) and the data comes right after that JSR, so if I can get the XT using ' then I can just add 3 to get the location of the data. That means, for TaliForth2, you could write a version like:

: TO ' 3 + ! ;

Note that the above places a VALUE into a variable (the standard behavior for the word TO). If you want to copy from one variable to another, you just have to get the data from the source variable first. That might look like:

: COPYTO @ ' 3 + ! ;

Your variables may be implemented differently, but often the data is right near the XT and you can just add the offset (as I did above) and then store your new value.

Thanks!

For some reason I got it in my head that the tick didn't work in word definitions. But that works.

BTW. What does XT stand for?

I have only read tick as pointing to the PFA (Parameter Field Address).

The only such limitations I can think of offhand are the IMMEDIATE compile-only words which cannot be used in interpretation mode, like DO...LOOP, BEGIN...UNTIL, etc..


"execution token," usually a word's CFA. (Caveat: I have not thought about how some of these things would work in a STC Forth.)


Tick looks up the CFA.

_________________
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The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

That could be why I am having trouble using it.

I confirmed that under the Forth I am using, it is returning the PFA.

Just another thing to add to the list to fix.

Worth checking. With FIG Forth, at least, it's the PFA that's left.

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

That is what is messing me up, in some of the primitive words, the code is not following the CFA.

Which means the PFA of some words are actually the word-length indicator of the next word.

Having the tick point to the CFA does make more sense.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Right.

But since, in Fig Forth anyways, the tick points to the PFA and not the CFA, this makes the tick useless for some words.

Not really. It's easy to get the cfa, at least in FIG Forth. The word CFA takes a pfa and returns the corresponding cfa. So, you simply choose to use either tick, or tick followed by CFA, to get what you want.

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

It's not so much a matter of "to get what you want", but more to understand when to use the CFA or the PFA.

I have come across a few words that require the address of the CFA, but have yet to really see any substantial requirement for the PFA.

Any examples where the PFA might be required would be appreciated.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

My bad! Didn't finish my sentence.

All these good examples are programmed into my Forth and nothing extra is required to use them.

I meant to say "Any examples where the PFA might be required with the use of the tick".