Remove car and cdr in favor of first and rest

[Kodiologist]

Closes #909.

[refi64]

It just feels weird to me that car and cdr were removed, yet there feels like a whole was left: now there's a head-tail function in one place, the removed macros redefined somewhere else, and also a bunch of (get x 0)s all over the place...

Not sure what a solution would be, but I still find this kinda weird...

[refi64]

Second and is redundant (though I feel like this might be easier to read if the section on empty literals was a separate sentence).

[refi64]

How about:

rest takes the given collection and returns an iterable of all but the first element.

[Kodiologist]

Most (get x 0)s could probably be replaced with first. I opted for a more literal translation so I didn't have to check that first doesn't prematurely eat up an iterator or something. Do you want me to use first where I can?

head-tail is an orthogonal bit of refactoring to the removal of car and cdr, but it was an obvious opportunity for refactoring, which I took when I noticed.

Incidentally, I hate iterables. In practice, the laziness is of no benefit, I have to convert them to a list or tuple in order to do most any operation on them, and I get bitten by subtle bugs that arise because iterators drop each element once it's accessed. Python 3 was in the wrong to make map, range, etc. produce iterables. I'm of half a mind to make Hy's iterable-producing functions (map, rest, etc.) automagically produce a collection instead when they're given a collection.

[refi64]

IMO iterables can be really useful (try filtering over a collection of ~2000 items and you'll see what I mean), but using them with collections can be annoying sometimes. In Python, it's less of an issue because those functions aren't even used too often, but in Hy, which has more of a functional leaning, it gets more annoying.

I kind of wish sometimes that Hy had a set of functions (e.g. map-c or something) that specifically return collections instead...

[Kodiologist]

I tend to use macros (e.g.) that are both anaphoric and always return lists.

You haven't approved this; what else needs to be done?

[gilch]

Incidentally, I hate iterables. In practice, the laziness is of no benefit, I have to convert them to a list or tuple in order to do most any operation on them, and I get bitten by subtle bugs that arise because iterators drop each element once it's accessed.

The solution might be the seq abstraction from Clojure hylang/hyrule#32.

[refi64]

Sorry, forgot about this. I guess the whole list vs iterator thing is more suited for another issue.

[Davoodeh]

I am a newbie just been playing around with Hy
Just saw this... It just feels off... Why would anybody want to possibly remove car / cdr from a Lisp?
I tried to can't there be an alias of some sort built-in Hy for this at least?
Not a fit to say here but : to cut would be another awesome alias

[Kodiologist]

@Davoodeh They were confusingly similar-but-not-identical-to first and rest; you couldn't use them in higher-order functions because they were macros rather than functions; and the names make no sense in Hy because there are no cons cells. If you really want them back, you can copy and paste the definitions into your own code.