Re: [External] : Re: Setting up abbrev

[Emanuel Berg <incal@dataswamp.org>]

Drew Adams wrote:

>> Only a pair is a list as well ...
>
> Yes.  But a list isn't a pair. ;-)

Every pair is a list but every list isn't a pair ...

Well, maybe one can think of a pair without order, i.e.
a set of two items?

The _ordered_ pair is the universal data structure that can
express anything then. The list is equally universal but the
ordered pair is the minimal working example, to speak with the
LaTeX guys ...

>> In practice - here, someone maybe disagrees? - but in my
>> experience I don't see why that should be used ...
>> 
>> And I don't know why it was ever essential to the point it
>> even got to symbolize Lisp on a couple of occasions?
>> 
>> Maybe that box diagram with arrows to make up a cons cell
>> link-list-fragment just looked neat and interesting ...
>
> 1. Key-value pairs are quite common - far beyond Lisp.

Sure, it's universal, and in particular Lisp is the most
universal of all programming languages ;)

> 2. A cons is a key-value pair.
>
> But the constructor function `cons' is more/other than that.
> As a key-value pair, (cons a (cons b c)) has key `a' and
> value key-value pair (b . c). Not your typical key-value
> pair use case - not typically thought of that way, at least.
>
> 3. A fundamental structure-building thingie in our universe
>    is the unary constructor, `s' (successor function).
>    Together with the nullary constructor, `0', it gives you
>    the Natural numbers - pretty foundational.
>
> The next structure-building thingie is the binary
> constructor, `cons'. Together with nullary constructor `nil'
> it gives you key-value pairs, or if you prefer, essentially
> all structures/constructions - sculptures of all sorts.
>
> Syntax-tree and function-application are fundamental
> structures for programs and (other) data. In Lisp, both are
> directly, unabashedly, handled as conses.
>
> If you want lists then you have conses. If you want trees
> then you have conses.
>
> As for the (a . b) _notation_: Why not? JSON uses `:'.
> Prolog uses `|'. Doesn't matter much what notation you
> choose. OOPs often use a dot notation for method
> application. Six of one; half a dozen of another...

Okay, but I still don't understand the benefit of using it in
practice compared to the list (a b)?

-- 
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