Re: [stack] What does "concatenative" actually mean?

On Mar 3, 2009, at 3:00 PM, William Tanksley wrote:

>> Id est replace words with their definitions.
>
> "A language is concatenative iff one can replace words with their
> definitions." I think that's at least CLOSE. You might also have to be
> able to replace a definition with the word as well -- it has to run  
> both
> ways. You also have to be "persnickety" that you're not allowed to
> rename anything during the replacement (i.e. you're not allowed to do
> beta reduction or alpha conversion).

You make it sound like Haskell might qualify. You can certainly  
replace words with their definitions in Haskell. Replacing expressions  
with the word that names them is possible as well for any "valid sub- 
program". For example, I can take '(\x -> foo x 10) y' and convert it  
to 'bar y' if 'bar' is defined as '\x -> foo x 10'. I could not,  
however, do something like replace 'foo x 10' with something because  
it is not a valid sub-program (as 'x' is not introduced anywhere).

I think the best definition of a concatenative language is as follows:

"All terms denote functions and their juxtaposition denotes  
composition."

Everything else follows from this. It also makes it clear why Haskell  
doesn't qualify.

- John