Gforth storing string values in variables

Question

I'm trying to store a string value into a variable. To define the variable, I use:

: define CREATE 0 , ;
define x

I can easily store an integer/float value to x using

10 x !

or

10.0e x f!

And to access it I use either @ or f@. Now I'm trying to store a string value:

s" hello world" x !

The problem with this is that it pushes two values to the stack (since it's a counted string) but x ! will only store the item on top, which is the length of the string. This is dangerous since the stack content might have been modified by the time x is referenced such that the address is not directly below the length (bad!), so type would fail. So my question is, is there a way to store both values (address and length) to x? Or is there a different data type/operand that would let me achieve this?

Any help is appreciated.

Answer 1

A lot of the things that you need to make this work are quite conveniently similar to what you have already.

You need a different version of define if you want to store two values in the things that you create with it;

: 2define create 0 , 0 , ;

Putting two at the start of a word is a convention that indicates it does the same thing as that word without the two but instead does it on double-cell things.

To use this you would write:

2define 2x
//Write something to 2x
s" Hello world!" 2x 2!
//Retrieve it and print
2x 2@ type

It is worth noting that the address that s" returns is not guaranteed to last the duration of the program and may be overwritten by a later use of s", to see a way to make a string variable that is guaranteed to last have a look at this answer https://stackoverflow.com/a/8748192/547299 (it is a bit long winded but there is a definition of a word called string which might be illustrative).