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07:23 tauntaun: We are taught to write + rather than (lambda (x y) (+ x y)).  What is the best name for this transformation?  Is it "currying"?  Or is it "beta-reduction"?  Or is it something else?
07:25 tauntaun: ...
07:25 jao: eta (not beta) reduction, i think.
07:29 tauntaun: thx
07:30 tauntaun: So would you say that currying is something like the inverse of eta-reduction?
07:32 bremner: isn't currying something to do with (lamda (x) (lambda (y) (+ x y))) ?
07:37 Lajla: No, currying is doing (+ 3) in a language that supports it
07:38 Lajla: currying is I believe an informal notion
07:38 Lajla: At least, when people say 'currying', they rarely seem to mean 'make a function curryable'
07:41 tauntaun: currying is very clearly defined.
07:41 tauntaun: The Racket implementation makes that clear.
07:41 tauntaun: The Racket documentation makes it clearer.
07:41 jao: that's partial application (+ 3)
07:41 tauntaun: jao: yes.
07:41 tauntaun: But my question is:
07:41 jao: currying is transforming an n-arg function into a 1-arg function
07:41 tauntaun: jao: yes again.
07:41 tauntaun: But my question is
07:42 tauntaun: Is it appropriate to think of currying as an inverse operation to eta-reduction?
07:48 Lajla: jao, pending literature, currying is the same thing as partial application.
07:48 Lajla: And 'partial application' is a very vague thing.
07:48 Lajla: the 'curryable +' is of course simply a one-argument function
07:48 Lajla: Its application is no more or less partial than that of any function which returns another function
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07:55 Lajla: tauntaun, to get to that point, I don't think it is.
07:55 Lajla: Curryizing + is (lambda (x) (lambda (y) (+ x y))
07:56 Lajla: Not (lambda (x y) (+ x y))
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10:39 clklein: Lajla: FWIW, in the definitions I've heard, curry : (a x b -> c) -> (a -> b -> c) and part-app : (a x b -> c) x a -> (b -> c)
10:39 Lajla: clklein, what does FWIW stand for?
10:39 Lajla: for what I ...?
10:39 clklein: Racket's `curry' does currying and partial application.
10:39 Lajla: For what it's worth?
10:39 clklein: yes, "for what it's worth"
10:39 Lajla: clklein, I guess the thing with terminology is that it's of course never objectively right and wrong.
10:40 Lajla: I've mostly seen 'currying' used in the same sense as partial application (which is a vague concept I would say)
10:40 tauntaun: Lajla: you keep saying currying is vague.  Could you please demonstrate with an example?
10:40 tauntaun: jao defined these terms very clearly earlier.
10:41 Lajla: tauntaun, I said partial application is vague
10:41 tauntaun: thank you.  Example?
10:41 Lajla: if you want to say that partial application is a different concept to currying it needn't be.
10:41 tauntaun: Explanation?
10:41 Lajla: tauntaun, give me a formal definition of partial application
10:41 Lajla: jao, defined what I would call 'make curryable
10:41 Lajla: Whic was not partial application
10:42 tauntaun: When an n-ary function is invoked with m arguments, with m < n.
10:42 Lajla: tauntaun, well, guess what, a curryable function always is single argument
10:42 tauntaun: we're not talking about curry.
10:42 Lajla: tauntaun, you know that in Haskell or lambda calculus all functions are single-argument right?
10:42 tauntaun: YES!
10:43 tauntaun: You seem to be avoiding the question.
10:43 Lajla: Well, if all functions are single argument
10:43 Lajla: then what does your definition say?
10:43 Lajla: Every function is 1 arry
10:43 Lajla: So M  cannot be < n
10:43 tauntaun: Oh God.
10:43 tauntaun: I can't believe you're fussing about this.
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11:13 jasond`: does anybody know why the turtles library produces occasional 1-pixel offsets?  example: http://98.129.169.48/tmp/turtles.png
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14:08 PLT_Notify: racket: master Matthew Flatt * ec2a917 (5 files in 2 dirs): Scribble: add `#:left?' optional argument to `margin-note'
14:08 PLT_Notify: racket: master Matthew Flatt * 4afd36c (3 files in 2 dirs): openssl: use libcrypto and libssl version 1.0 if available ...
14:08 PLT_Notify: racket: master commits 68b5d2a...4afd36c - http://bit.ly/fc4UOp
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18:35 danger_: so i have been working on this simple transposition prog could some one tell me why my append isnt working?
18:36 danger_: (define stuff   (lambda (x y)            (if (null? y) 0)       (if (not (null? (car y))) (stuff (append x (list (map car y))) (map cdr y)))          ))            (define x '())  (define y '(( 1 2 3 4 )( 4 5 6 7 )( 7 8 9 0 ))) (stuff x y)
18:36 danger_: any one here?
18:38 (join) jonrafkind
18:38 danger_: ...
18:40 danger_: do i not know something or do people not talk
18:51 jonrafkind: talking is forbidden
18:51 danger_: i see
18:52 danger_: so i guess no one could answer my questions here
18:52 danger_: know any place were i could ask them
18:52 jonrafkind: whats your question
18:53 danger_: i was haveing an issue with the append statment
18:54 danger_: heres my code
18:54 danger_: (define stuff   (lambda (x y)            (if (null? y) 0)       (if (not (null? (car y))) (stuff (append x (list (map car y))) (map cdr y)))          ))            (define x '())  (define y '(( 1 2 3 4 )( 4 5 6 7 )( 7 8 9 0 ))) (stuff x y)
18:54 danger_: it works fine if you look at the debug
18:54 danger_: sept for the append
18:55 danger_: the most frustrating mystery indeed
18:56 jonrafkind: did you mean to put a ) after the 0 in (null? y) ?
18:56 jonrafkind: that makes a one-armed if
18:57 danger_: what do you mean one armed?
18:57 jonrafkind: i mean there is no else branch, just a then
18:57 jonrafkind: its usually (if <condition> <then> <else>)
18:57 jonrafkind: you just have (if <condition> <then>) with no <else>
18:58 danger_: mmm ok so i tried deleting that check
18:58 jonrafkind: it looks like you want to use cond instead
18:59 jonrafkind: how are you running this prorgam?
18:59 danger_: the (if (null? y) 0)
18:59 danger_: and i get the same results
18:59 jonrafkind: what result exactly
18:59 danger_: nothing xD
18:59 danger_: nothing prints
18:59 jonrafkind: how are you running this program?
18:59 danger_: everything appears to work tell it gets to the append statmetn
19:00 danger_: im running it in racket
19:00 jonrafkind: in a student language?
19:00 danger_: yes
19:00 danger_: essentials of prog lang 3
19:00 jonrafkind: do you have a description of `cond' around
19:01 danger_: yes
19:01 jonrafkind: do you understand how to use it?
19:01 danger_: i believe so
19:01 danger_: (cond (expression))
19:02 danger_: thats an abridged version
19:02 jonrafkind: well.. its (cond (condition expression) ...)
19:03 danger_: yep
19:03 danger_: just edited
19:03 danger_: (define stuff   (lambda (x y)            (cond       ((not (null? (car y))) (stuff (append x (list (map car y))) (map cdr y)))          )))
19:03 danger_: get the same results
19:03 danger_: it works in apperence when you look at the debug
19:03 danger_: but it doesnt ever append anything to the x
19:04 jonrafkind: what if (car y) is null?
19:04 danger_: if car y is null it just stops
19:04 danger_: meaning if the list is empty it shouldnt recurse again
19:05 jonrafkind: so whats the return value if car y is null?
19:05 jonrafkind: do you realize that append does not mutate x?
19:05 jonrafkind: rudybot: (define x '(1))
19:05 rudybot: jonrafkind: your sandbox is ready
19:05 rudybot: jonrafkind: Done.
19:06 jonrafkind: rudybot: (append x '(2))
19:06 rudybot: jonrafkind: ; Value: (1 2)
19:06 jonrafkind: rudybot: x
19:06 rudybot: jonrafkind: ; Value: (1)
19:06 danger_: wait im confused
19:06 danger_: so why doesnt the append take the x list and add the y to the end
19:07 danger_: of x*
19:07 jonrafkind: it does but it returns a new list, it does not modify the x variable
19:08 jonrafkind: you want something like in C, x = append(x, y); thats not how it works in scheme
19:08 danger_: mmm i thought about that too but as you see it should transfer it to the next iteration
19:08 jonrafkind: it does
19:08 jonrafkind: now what happens when (car y) is null?
19:09 danger_: the way i assume it works is: (append x y) (define x '(3)) (define y'(4)) the new x should be (3 4)
19:10 jonrafkind: thats not how it works
19:10 danger_: mmmm
19:10 jonrafkind: (append x y) makes a new list
19:10 jonrafkind: it does not modify x
19:10 danger_: le sigh
19:10 jonrafkind: by 'new x' do you mean after recursion?
19:10 danger_: no i mean its added to the old definition
19:11 danger_: but i see where im wrong
19:11 danger_: how can i fix this append issue
19:11 danger_: meaning how can i add something to a current list
19:12 jonrafkind: you need to define your program in terms of recursion (which you already have done) but you haven't fully grasped how to pass values in a recursive program
19:12 jonrafkind: you dont need to add things to the current list, you can return a new list
19:12 danger_: mmmm
19:12 danger_: ...
19:13 jonrafkind: what is 'stuff' supposed to return?
19:13 danger_: ok
19:13 danger_: stuff should transpose the matrix
19:13 danger_: i just dont have the best name xD
19:13 danger_: i suppose i could change it to transpose
19:13 jonrafkind: ok if (car y) is not null it returns the intended thing, right?
19:14 danger_: yes
19:14 danger_: i think
19:14 jonrafkind: ok so now if (car y) is null what odes it return
19:14 danger_: it thows an error in runtime
19:14 danger_: wait
19:14 danger_: one sec
19:14 jonrafkind: can you cahnge it so that if (car y) is null it returns the intended result?
19:15 danger_: what the car y is suposed to do is check to see if the y matrix is empty
19:15 danger_: if it isnt empty it should do the append and recurse
19:16 jonrafkind: so what if it is empty?
19:16 danger_: it just ends i suppose (skips the statment)
19:16 jonrafkind: and then what
19:17 danger_: i would like it to print the transposed matrix
19:17 danger_: but right now nothing happens
19:17 jonrafkind: if the function doesn't return anything how will you get the matrix to transpose?
19:18 jonrafkind: if none of the cond clauses execute you get 'void' back
19:18 danger_: so what your saying is i should have a "print statment" on a void
19:19 jonrafkind: you can try it, but thats not what im saying
19:19 jonrafkind: stuff(x) will return the transposition of `x' right?
19:20 danger_: its display right?
19:20 danger_: yes
19:20 jonrafkind: ok so you make a recursive call there if y is not empty, so you do stuff(x,y) = stuff(append(x, ...), ...), right?
19:20 danger_: oh shit it worked xD
19:20 danger_: with the display
19:20 danger_: lol
19:20 danger_: thanks alot
19:20 danger_: a lot*
19:20 danger_: not the animal
19:21 danger_: xD
19:21 jonrafkind: well yes it will work but your program is still wrong
19:21 jonrafkind: try printing the result of `stuff'
19:21 jonrafkind: (display (stuff x y))
19:21 danger_: in stuff?
19:21 jonrafkind: no outside stuff
19:21 danger_: kk
19:21 danger_: still works
19:21 jonrafkind: no, you still have the display inside stuff
19:21 jonrafkind: take that out
19:21 danger_: kk
19:22 danger_: void
19:22 jonrafkind: yes
19:22 jonrafkind: now look at this, stuff(x, y) =  stuff(append(x, ...), ...), right?
19:22 danger_: im not sure i understand what you mean
19:23 jonrafkind: its the recursive call you are making. do you know what recursion is?
19:23 danger_: yes
19:23 danger_: ok ok i seee
19:23 danger_: xD
19:23 jonrafkind: so that equivalence is made when (car y) is not null, right?
19:24 danger_: ok..
19:24 jonrafkind: so then what if (car y) is null? what is stuff(x, y) ?
19:25 danger_: well x is always null if you look at the debug and y is (()()()())
19:26 jonrafkind: what is the result of (stuff '(1) '(())) ?
19:26 jonrafkind: what will stuff return?
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19:26 danger_: well it would return nothing
19:26 danger_: nothing would happen
19:26 jonrafkind: so is nothing the transposed matrix?
19:27 danger_: yes beacuse the first argument should always be empty and thus when a empty matrix is transposed it will be nothing
19:27 danger_: its transposing y
19:27 jonrafkind: i mean, (stuff x y) = (stuff (append x ...) null) = void, right?
19:27 danger_: i was trying to put it in x
19:27 danger_: yes
19:27 jonrafkind: so (stuff x y) = void, is that what you want?
19:28 danger_: thats fine by me ... what i wanted it to do was put the transpose of y in to x
19:28 danger_: so i could print out x
19:28 jonrafkind: you cant do that
19:28 jonrafkind: you can only return new values of x
19:28 (quit) shachaf: Ping timeout: 272 seconds
19:28 danger_: i see
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19:29 jonrafkind: outside of stuff do (display x), it will still be '()
19:29 jonrafkind: the x variable inside stuff is a different variable from outside
19:29 danger_: thats alright with this but is there a way where i could get it in x for further refrence
19:29 jonrafkind: which x, the one outside?
19:29 danger_: yes
19:29 jonrafkind: you could do (set! x (stuff x y))
19:30 danger_: ah set
19:30 (quit) sstrickl: Quit: sstrickl
19:30 jonrafkind: a better way is (let ([x (stuff x y)]) (display x)
19:30 danger_: i was just about to learn that one
19:30 jonrafkind: generally mutation is bad
19:30 danger_: i seriously have it on my list next
19:30 danger_: of things to do
19:30 jonrafkind: you should take it off your list
19:30 danger_: noted
19:30 danger_: notted*
19:31 danger_: ffff
19:31 danger_: i can never spell
19:31 danger_: so i have one last question
19:31 danger_: well 2
19:31 danger_: how old do you think i am
19:31 danger_: and whats your background?
19:32 jonrafkind: are these homework questions?
19:32 danger_: no lol just mine
19:32 jonrafkind: im a graduate student
19:33 danger_: fun stuff
19:33 danger_: im a senior :P about to be a grad student specializing in security
19:33 danger_: in cs
19:34 danger_: well thanks for your help
19:36 jonrafkind: word
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20:03 greg___: Hello?
20:04 jonrafkind: hi
20:06 greg___: This is the chat room for programing in scheme, right?
20:06 jonrafkind: yea
20:08 greg___: I'm trying to figure out how to iteratively append a list of values from a list of dotted pairs (using the x coordinate of the pair)
20:08 greg___: Newbie
20:09 tauntaun: you mean '((a . b) (c . d) (e . f)) => '(a b c d e f) ?
20:09 jonrafkind: i thought he meant => '(a c e)
20:09 tauntaun: aH
20:09 tauntaun: (curry map car)
20:09 greg___: Yes, what jonrafkind said
20:10 jonrafkind: (map car x)
20:11 greg___: so given the list pt-list => ((a . b)(c . d)(e . f)), (map car pt-list) will return the list (a c e)?
20:11 tauntaun: y
20:12 greg___: aha cool. That makes my life a whole lot easier
20:12 greg___: Thank you
20:13 greg___: Have a nice night
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20:36 burtreynolds: sup all?
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20:42 tauntaun: hi burtreynolds
20:45 burtreynolds: It's actually greg again. I'm looking for a way to append a list as before (the x values from a list of dotted pairs) but without using (map car p)
20:45 tauntaun: can you say why?
20:46 tauntaun: mapping car strikes me as the most concise solution
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20:47 burtreynolds_: My apologies my browser crashed momentarily
20:47 tauntaun: did you catch my last two lines?
20:47 burtreynolds_: I'm sorry no
20:48 tauntaun: I'm just wondering why mapping car isn't good enough.
20:50 (quit) burtreynolds: Ping timeout: 272 seconds
20:51 burtreynolds_: It's gonna sound stupid, but its part of the assignment that we can't use it.
20:51 burtreynolds_: I'm a student yet
20:51 (nick) evhan_ -> evhan
20:53 tauntaun: Doesn't sound stupid at all, but without map you'll have to write an explicitly recursive function.  Do you know how to write one that simply copies a list?
20:53 burtreynolds_: No.
20:54 tauntaun: (define (copy-me ls) (if (null? ls) '() (cons (car ls) (copy-me (cdr ls)))))
20:54 tauntaun: rudybot: (define (copy-me ls) (if (null? ls) '() (cons (car ls) (copy-me (cdr ls)))))
20:54 rudybot: tauntaun: your sandbox is ready
20:54 rudybot: tauntaun: Done.
20:54 tauntaun: rudybot: (copy-me '(1 2 3))
20:54 rudybot: tauntaun: ; Value: (1 2 3)
20:55 tauntaun: burtreynolds: If you can understand copy-me, you'll be able to do your assignment without any problems.
20:55 tauntaun: To understand copy-me, try executing it on paper on several lists, starting with the empty list, then a one-element list, then a larger list.
21:00 burtreynolds_: Ok i see, I see...
21:00 burtreynolds_: Now is there a way to convert a list to a string so that I may use a 'max' procedure on it?
21:11 tauntaun: burtreynolds_: not sure what you mean.  Could you give an example?
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