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newLISP the true champion of homoiconicity

Name: Anonymous 2012-11-10 10:11

Can your Lisp do this, /prog/?

(define (plus-minus a b)
  (begin
    (setf (nth '(1 2 0) plus-minus) (if (= (nth '(1 2 0) plus-minus) -) + -))
    (+ a b)))

(plus-minus 10 2)
8
(plus-minus 10 2)
12

newLISP treats code literally as data unlike Common Lisp or Scheme.

Name: Anonymous 2012-11-10 10:13

Now let's see how useful that is

Name: Anonymous 2012-11-10 10:17

Only the most unimaginative members of the herd can murmur Now let's see how useful that is

Name: Anonymous 2012-11-10 10:20

>>3
You have no better answer? Then I have no reason to believe it is useful.

Name: Anonymous 2012-11-10 10:23

>>1
THIS IMPURITY MUST BE PURGED!

Name: Anonymous 2012-11-10 10:45

Can you use a more interesting example? I could just do this if I wanted a oscillating function:

(let (p) #'(lambda () (progn (setf p (null p)) (if p #'+ #'-))))

Name: Anonymous 2012-11-10 13:51

>>6
Thats ugly as fuck.

Name: Anonymous 2012-11-10 14:19

>>7
And how is that at all dissimilar to the very concept of impure functions?

Name: Anonymous 2012-11-10 18:49

>>2,6

This is arbitrary code manipulation at the syntax level at run time. Consider an algebraic profiling optimizer.

Name: Anonymous 2012-11-10 19:09

>>4
I agree with you. I also have no imagination and cannot fathom any practical use for this.

Name: >>6 2012-11-10 19:18

>>9
Don't worry, I like it. A more interesting example is what I would have wanted.

Name: Anonymous 2012-11-10 19:21

some of the stack based languages have a similar abstraction of functions being flat arrays of constants. But it isn't parsed so it isn't as easy to use well.

Name: >>12 2012-11-10 19:22

err, not really an abstraction. Just a level of accessibility normally not granted.

Name: Anonymous 2012-11-10 20:37

I wish to be achieve macro satori, what must I read?

Name: Anonymous 2012-11-10 20:47

>>14
There isn't that much to them. Just use them a few times and then you will feel the satori building within you, just waiting to abstract and factor enterprise design patterns away into self implemented language features. It doesn't need to be a lisp either, but it should have a comparable macro system.

Name: Anonymous 2012-11-10 20:57

http://cl-cookbook.sourceforge.net/macros.html
(defmacro setq2 (v1 v2 e)
   (let ((e1 (comtran e)))
      (list 'progn (list 'setq v1 e1) (list 'setq v2 e1))))

(defun comtran (exp) ...) ;; Right!

Wait, what the fuck?  Macro setq2 just uses procedure comtran without any issues?  But comtran isn't even defined yet!  What if someone does something evil/stupid like (let ((comtran evil-procedure)) (setq2 x y z))?  What if comtran has an instance of setq2 in it?  Is it just me, or macroexpansion-time stuff should live in its own namespace?

Name: Anonymous 2012-11-10 21:54

Name: Anonymous 2012-11-10 22:14

>>16
Evaluation time of macros is a bit confusing. Don't worry, you'll get it soon.

Name: Anonymous 2012-11-10 23:21

http://www.youtube.com/watch?v=HM1Zb3xmvMc

Name: Anonymous 2012-11-11 7:12

>>19
https://www.youtube.com/watch?v=9WtzffIOoNY&feature=endscreen

Name: Anonymous 2012-11-11 10:51

>>20
Terrible!

Name: Anonymous 2012-11-11 11:43

>>22
HOLY FUCK!!!!!!!!!!!!!!
dubs

Name: Anonymous 2012-11-11 12:22

>>18
No, it's very confusing. :/

Name: Anonymous 2012-11-11 13:02

>>23

try this one on for size.

https://dis.4chan.org/read/newpol/1350310688/34

Name: Anonymous 2012-11-11 15:35

>>24
That still doesn't enlighten me as to how macros are supposed to be able to use regular functions (not defined in some sort of macrospace).

Name: Anonymous 2012-11-11 15:43

>>25

If mf is a function and m is a macro defined as:

(defmacro m (&rest args)
  (apply mf args))

Then the following are equivalent:


(m 2 3 4)
(eval (mf 2 3 4))


(m (* 5 6 (/ 7 8)) (eat apple))
(eval (mf '(* 5 6 (/ 7 8)) '(eat apple)))

Name: >>26 2012-11-11 15:49

In other words, mf is a function that takes a syntax tree as an argument and produces another syntax tree for evaluation.

Name: Anonymous 2012-11-11 16:27

>>26
Yes, but mf is a regular function!  What if yo do something like

(defun mf (...) ...)

(let ((mf something-else))
  (defmacro m (&rest args)
    (apply mf args)))

Name: >>28 2012-11-11 16:27

*you

Name: Anonymous 2012-11-11 16:32

>>28
In that case the macro m has lexical scope, and it uses the mf function defined in the let statement for its code transformer. It is powerful to let any user defined lisp function to assist your macro. And we are creeping up on first class macros, but we haven't gotten there yet.

Name: Anonymous 2012-11-11 16:35

]=> (define plus-minus
  (let ((plus? #t))
    (lambda (a b)
      (set! plus? (not plus?))
      ((if plus? + -) a b))))
plus-minus
]=> (plus-minus 10 2)
8
]=> (plus-minus 10 2)
12

Name: Anonymous 2012-11-11 16:44

(eval (macro-function ...))

Name: Anonymous 2012-11-11 17:27

>>30
Wow, I can't believe that actually works.  I'm going to go ahead and try to write a macroexpand function in terms of eval and apply.

Name: Anonymous 2012-11-11 17:40

>>33
Wow, I can't believe I was alive to witness those awesome dubs.

Name: Anonymous 2012-11-11 18:25

REPL MY ANUS

Name: Anonymous 2012-11-11 21:44

And we are creeping up on first class macros, but we haven't gotten there yet.
Why not just use Factor? It's had first class macros for years.

Name: Anonymous 2012-11-12 1:06

Explicit macros are a leaky abstraction.

There, I said it.

Name: Anonymous 2012-11-12 1:44

>>37

Making them explicit helps with efficiency in the implementation. To maintain performance, they should all be expanded at compile time, and this would be hard if they weren't explicit. Not to mention a macro getting into a place where you only wanted a function would be a hard bug to figure out. But like all things that help performance, it must also cut down on expressive power and possibilities.

Name: Anonymous 2012-11-12 2:11

>>38
>>37 didn't say that the leakiness isn't justified.

Name: 33 2012-11-12 4:50

Little did I know that my endeavour would slowly drive me to madness.  Seriously, what the fuck.  I need some good references on macro magic, and maybe a hug or two.
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