Forth: associate a name with a memory address

Question

I use a word ->list that creates and returns an address. I don't always need to associate this address with a variable name, but I'd like that to be possible. For the moment, if I want to do so, this look like this:

.s <0>  ok
1 2 3 3 ->list .s <1> 140318466418488  ok
VARIABLE mylist  ok    
mylist ! .s <0>  ok  
mylist @ . 140318466418488  ok
mylist @ @ . 1  ok   
mylist @ 1 cells + @ . 2  ok
...

This provides an indirect addressing to access elements in ->list adress. Is it possible to create a variable which address is an already known address?

There is a bug in your code. The word create does not reserve any units in the data field, you have do it by yourself, e.g.: CREATE mylist 1 cells allot or CREATE mylist 0 , — ruvim
– ruvim, Commented Jul 16, 2023 at 14:06

ruvim · Accepted Answer · 2023-07-16 13:59:57Z

5

To associate a number (an address as well as any other number) with a name you can use constant. In your case:

1 2 3 3 ->list constant mylist
mylist @ . \ "1"

Is it possible to create a variable which address is an already known address?

In Forth, a variable is actually a constant that returns an address.

For example, the word variable can be defined as follows:

: variable ( "name" -- )
  align here 0 , constant
;

So if you have the address of an already reserved cell, you can just use constant. For example:

align here 123 ,  constant myvar
myvar @ . \ "123"
456 myvar !
myvar @ . \ "456"

answered Jul 16, 2023 at 13:59

ruvim

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