Re: [stack] language hierarchy

On Dec 5, 2007, at 10:13 AM, William Tanksley, Jr wrote:

> Hmm. Okay, I think I get it. Review: composable means that function
> composition is available and capable of forming interesting programs.
> Concatenative means that function composition is the default operation
> (performed by merely concatenating functions).

No, not quite. Composable means composing functions is the only way to  
write programs. Joy works this way. Concatenative languages are  
composable languages with Joy-style syntax. I do not know of any  
language that is composable and not also concatenative; It's the  
obvious syntax to use. However, you can imagine such languages fairly  
easily.

>> I don't think there's anything composable about Haskell, strictly
>> speaking. The compose operator in Haskell is really just a function
>> with infix syntax that operates on functions /as values/ via function
>> application.
>
> Perhaps, but the language supports that composition on such a
> fundamental level that it's hard to identify it as NOT part of its
> syntax.

It isn't any more part of the syntax than 'apply' is part of Cat's  
syntax.

> A number of different subsets of Haskell can be constructed
> that form a composable language -- for example, consider a stack
> monad. At least if I'm reading your definition of 'composable'
> correctly.

No, I don't think you are. The compose function in haskell operates on  
values via application, not on functions directly as it does in Joy.  
Haskell is a functional language, not a function-level language like FL.

>> This is something you can add to most any vaguely
>> functional language:
>>        (define (compose f g) (lambda args (f (apply g args))))
>
> Sure; and if you can define that as infix, your language has
> superficial support for composability.

Neither infixness, nor any other syntax-related feature, has nothing  
to do with my definition of 'composable'.

>  think your definition is adequate, so let's go forward with it.

Hm. Well, I will at least!

- John