Re: [stack] Properties of Concatenative langauges and Forth

On Jan 2, 2009, at 11:50 AM, William Tanksley, Jr wrote:

> Christopher Diggins <[email protected]> wrote:
>>
>
>> f g h <=> (f g) h <=> f (g h)
>> Does Forth have this property?
>
> Yes, except where you're using macros or other compiling words.

I think macros and compiling words get a pass. Saying they don't  
wouldn't be much different than saying Haskell isn't purely functional  
because top-level definitions can alter the meaning of other parts of  
the program. Forth's dynamic nature obscures this a bit, but I think  
it's essentially the same thing.

The concatenative requirement is sensibly limited to expressions  
within the language. In certain cases, it might be required to expand  
the macros to get the concatenative expression. I think we can  
sensibly talk about a concatenative language "plus macros". Factor  
offers a good example; just because there exists a macro for locals  
doesn't make the language non-concatenative.

> It's kind of odd to say that Postscript and Forth are Joy-like.

Indeed.

- John