Re: [stack] impure concatenativity: let without translation

On Mar 19, 2008, at 19:11 , John Nowak wrote:
>
> On Mar 19, 2008, at 4:51 PM, Joe Bowbeer wrote:
>
>> On Wed, Mar 19, 2008 at 11:58 AM, John Nowak wrote:
>>
>>> Postfix, as are *all* procedures. Only special forms are infix.
>>> Perhaps this is a better declaration form:
>>>
>>>    (define (a b c quad)
>>>       ...)
>>>
>>> - John
>>>
>>
>> Better.  Better yet is:
>>
>>   (...
>>      (a b c quad) define)
>>
>> This maintains a consistent right-to-left reading direction.  If
>> postfix is
>> the "right thing," there's no such thing as too much, right?
>
> There is. Special forms and macros need access to the entire tree to
> do their work. If you were to put 'define' at the end, then there's no
> way for it to act on the tree (without some bizarre backtracking).
> Keep in mind that even [a b c] is really (lambda () a b c). Putting
> meta-level things like 'define' and 'let' up front also aids in
> readability.
>
>> Naive question: Is there any reason why concatenative languages are
>> (uniformly) postfix?  Would prefix work just as well, pushing
>> elements onto
>> the stack from right to left?
>
> Let's say these two are equivalent:
>
>     -- postfix
>     hypot -> sqr swap sqr + sqrt
>
>     -- prefix
>     sqrt + sqr swap sqr <- hypot

I'm partial to the syntax I'm using in ACL:

[sqr swap sqr + sqrt] -> hypot

This reads left-to-right and solves the problem of the
as yet undefined symbol, hypot, which is read by ->

Actually, I use "def" instead of "->" for clarity but the
meaning is the same.
--
don



> Sure, both mean the same thing, but which is easier to read (provided
> you're used to reading left to right)?
>
> - John
>
>
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