Re: [stack] function/object ambiguity + quotation alternative

On Mar 3, 2009, at 12:06 PM, William Tanksley wrote:

>> The nesting in
>> Scheme helps visually and things remain mostly understandable even if
>> you don't know the arities of all the functions involved. That's only
>> my opinion of course; I've not launched a study to determine if this
>> goes for most people, although I suspect it does.
>
> Forth is the only concatenative language we've discussed that lacks
> nesting. Why would you list "nesting" as an advantage of associative
> languages?

I was being sloppy. I've certainly proposed "concatenative" languages  
with as much nesting as you find in Scheme.

I really was meaning to compare idiomatic ways of writing code in  
concatenative languages. Take the following code for example:

    foo bar [baz] dip quux

You will, in practice, get concatenative code like this. Now compare  
to what might be the applicative equivalent:

    (let ([(x y z) (foo input)]
          [(b c)   (baz y z)])
      (quux (bar x) b c))

Here, it's clear that foo returns three values, bar only cares about  
one, baz only cares about two, bar uses the first result of foo, baz  
uses the second two, baz is independent of bar, quuz uses one result  
from bar and two from baz, etc.

Getting all of this information out of the concatenative version isn't  
possible. Does bar use one value? Two? More? What about quux? Does baz  
depend on the result of bar? All of this is clear in the applicative  
version but not the stack-based concatenative version.

Again, in practice, I occasionally find this difficult when writing  
code quickly to prototype something. If you don't, then I certainly  
won't call you a liar. Perhaps I just have Scheme burned into my head.

- John