[Xpath-ng] List constructor syntax

[David Carlisle]

> I withdrew my
> objection to treating them the same -- did anyone else have one?

me, I think.

If I have a list of lists

(list (list 1 2)  (list 3 4))

Then I can make a list of all their first elements, something like

(mapcar 'car (list (list 1 2)  (list 3 4)))
(1 3)

(It's useful if your mail client has a built in lisp system:-)

But how's the (mapcar 'car  function supposed to work if one of the
child lists was a singleton, it gets automatically flattened and then
presumably errors as you can't apply car to a non list.

So a simpler example: Is

(car (list 1))

which I'd expect to be 1

the same as 

(car 1)

which is 

Wrong type argument: listp, 1  ??


I'd have no problem with it being part of the function call semantics
that any function expecting a value can be passed a singleton list,
but I don't think I'd like to see singleton lists actually flattened in
the data model.


David

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