Re: [stack] initial stab at a wikipedia entry

On Jan 2, 2009, at 9:50 AM, William Tanksley, Jr wrote:

> Not true -- a variable can be modeled (loosely) as an implicit
> function of time. Forth provides local and global variables; locals
> seem to make a language less concatenative, while globals don't hinder
> it so much. (Naturally, globals have other problems.)

Global variables can be treated as functions that read/write some  
state that gets passed through the program thanks to the monoidal  
nature of things. Local variables cannot; their scopes are local and  
hence you can't factor out code that references a local variable. The  
only way of explaining locals is in terms of substitution.

I'm not sure if you think my explanation above rules out locals. If  
not, perhaps it would be beneficial to include "factorability" as part  
of the definition of concatenative languages, e.g. 'f g h == f i where  
i == g h'. I was hoping to get away without having to explicitly  
mention this (and hence doubling the length of the definition).

> I'm also thinking about expanding the point about monoids a bit. We
> have a little to be said on that issue that can't be said on the page
> about monoids.

You're right. My only problem is trying to find something to cite in  
the logs. I'll come up with something most likely...

- John