[Jprogramming] AoC 2016 day 10

['Jon Hough' via Programming]

I wrote an Object Oriented implementation of a hashmap a while ago: https://github.com/jonghough/msgpack-j/blob/master/hashmap.ijs

It's not brilliant but I have used it for some things. 

e.g.

hm =: '' conew 'HashMap'
set__hm (1; 'hello')
get__hm 1

It can also contain other hashmaps as values -- although I had to use a horrific workaround because J has no object introspection (that I know of), so 
you can't differentiate between a boxed literal and an object reference.

--------------------------------------------
On Mon, 12/12/16, Moon S <moon.aka.sun at gmail.com> wrote:

 Subject: [Jprogramming]  AoC 2016 day 10
 To: "programming" <programming at jsoftware.com>
 Date: Monday, December 12, 2016, 1:53 AM
 
 I won't lie, first I wrote that
 solution in Python. It's much easier and
 faster. Then the program was translated to J. The biggest
 problem was that
 J didn't have dictionaries. While even K has! And sparse
 arrays don't
 support strings or boxed values. Argh. And we are at the end
 of year 2016!
 Anyway, we deal with small numbers, it's quite suitable to
 grow an array
 when we need to insert some value there with an index a bit
 greater than
 the length of the array. We could also allocate some big
 arrays, or just
 bigger than input, or to calculate the sizes based on the
 input. Well, it's
 possible, yes. But pretending to deal with dictionaries
 looks more pleasant
 to me. So it was finally, the J solution for Day 10.
 
 t =: cutLF CR-.~fread '10.dat'
 
 'E O B' =: 0 0 1 NB. empty value; what:Output, what:Bot
 b =: 0 6$0 NB. i-th bot: [lo-what lo-index hi-what hi-index
 slot1 slot2]
 o =: i.0 NB. outputs, empty vector at first
 
 NB. first we build the bot net
 3 : 0 t
   for_s. y do. s =. ' 'cut >s
     if. -. 'bot'-:>{.s do. continue. end. NB.
 do only bots
     'k lk hk' =.".>1 6 11{s NB. all numbers
 from string
     lo=.('bot'-:> 5{s){O,B
     hi=.('bot'-:>10{s){O,B
     if. k>:#b do. b =: b,((>:k-#b),{:$b)$0
 end. NB. expand b if needed
     b =: (lo,lk,hi,hk,E,E) k}b
   end.
 )
 
 pv =: 4 : 0 NB. pass value; x - value to set, y - pair
 what,index
   k=.{:y
   if. O={.y do. NB. output, set value in o
     if. k>:#o do. o =: o,(>:k-#o)$E end. NB.
 expand o if needed
     if. E~:k{o do. exit#echo 'output already set
 ',"k,k{o end.
     o =: x k}o
   else. NB. B - bot, set 1st slot, or 2nd slot and then
 propagate value
     if. k>:#b do. exit#echo 'no such bot ',":k
 end.
     'lw lx hw hx s1 s2' =. k{b
     if. s1=E do. NB. both slots are empty, let's
 set the 1st
       b =: x (<k,4)}b
     else.
       if. s2~:E do. exit#echo 'no empty slot
 ',":k,v,s1,s2 end.
       b =: x (<k,5)}b
       lv =. x <. s1
       hv =. x >. s1
       if. 17 61 -: lv,hv do. echo k end. NB.
 part 1: catch what was asked!
       lv pv 0 1{k{b
       hv pv 2 3{k{b
     end.
   end.
 )
 
 NB. then we spread values
 3 : 0 t
   for_s. y do. s =. ' 'cut >s
     if. -. 'value'-:>{.s do. continue. end. NB.
 process only values
     v pv B,k [ 'v k' =.".>1 5{s
   end.
 )
 
 echo */0 1 2{o NB. part 2: multiply outputs
 
 exit 0
 
 It's rather long, but easy to understand, I hope. If you
 remove comments
 and rearrange some pieces of code, it'll be down to 720+
 chars and will fit
 one screen.
 
 The idea of the solution was first to build the whole
 network of bots, i.e.
 to have them all with their connections to other bots, but
 without any real
 values yet; then we start to put values to the bots and
 propagate those
 values to other bots and to the output. Usually the puzzles
 of AoC allow
 such simple solutions - all the data is correct, no
 conflicts, no races in
 schemes, all will be perfect in the end. So such a solution
 works.
 
 Then it comes the challenge -- to make it all J-style, all
 tacit and magic
 :)
 Well, there's still left one explicit definition, I guess it
 would've been
 too complicated if it was tacit.
 
 The basic ideas are the same, to build the bot net and put
 the values
 there. On the second stage the reduce is used. J doesn't
 allow arbitrary
 types for '/' or an initial/state value of different type,
 but here boxes
 come to the rescue - we can put anything in the boxes and
 work with them as
 with simple values.
 
 t =: cutLF CR-.~fread '10.dat'
 NB. verbs -----------------------------------
 onlybots =: #~ ('bot'-:3{.>)"0
 onlyvals =: #~ ('val'-:3{.>)"0
 parsebot =: [:".[:>1 4 5 8 9{[:cut('to output';'0';'to
 bot';'1')rplc~>
 parseval =: [:<[:".[:>1 5{[:cut >
 val2out =: ([:{.])`([:<_1,5<.[:{:])`[ } NB. save value
 to output = last
 bots item
 val2slot1 =: ([:{.])`([:<4,~[:{:])`[ }
 val2slot2 =: 4 : 0
   if. 17 61 -: lh=./:~ ({.y),4{(k=.{:y){x do. echo {:y
 end. NB. part 1
 answer
   ((({.y)(<k,5)}x)pv({.lh),0 1{k{x)pv({:lh),2 3{k{x
 NB. set slot2 and pass
 both values
 )
 val2bot =: val2slot2`val2slot1 @. (0=4{([:{:]){[) NB. choose
 slot
 pv =: val2out`val2bot @.(1{]) NB. pass value
 av =: [:< ([:>]) pv 1j1 1#!.1[:>[ NB. apply value
 to bots
 NB. nouns -----------------------------------
 bots =: (0 0,~}.)"1 /:~ parsebot"0 onlybots t NB. get all
 bots from input
 vals =: parseval"0 onlyvals t       
          NB. get all vaules
 echo */3{.{:> av/ |.(bots,0);vals     
        NB. apply values to bots;
 part 2 output
 exit 0
 
 I don't know if it's really readable. Anyway it works.
 
 Enjoy :)
 
 P.S. what was interesting there: v1`v2 @. vt, v1`v2`v3 }, /
 over boxes, AjB
 #!.C.
 
 Georgiy Pruss
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