Thank you very much! Sorry I cannot answer something about it right now,
because I need much more time to read it and to understand.
But I see none of < > and { :)
Thank you,
On Wed, Oct 2, 2013 at 10:04 PM, Dan Bron <[email protected]> wrote:
> Alexander (inv2004) wrote:
> > Description I am trying to calculate:
> > http://www.usacycling.org/news/user/story.php?id=580
> > source data: https://dl.dropboxusercontent.com/u/34917039/2013.txt
> > J source: https://dl.dropboxusercontent.com/u/34917039/1.j
>
> I knocked together an implementation in J (based on my perhaps-mistaken
> understanding of your problem):
>
>
> http://jsoftware.com/svn/DanBron/trunk/uncategorized/scoreRoadRace.ijs
>
> It didn't take very long to code, but unfortunately it would take much
> longer to explain it in prose. Also, the style is very peculiar to me,
> which means it's dense, and uses some sneaky tricks, so even veteran J
> programmers may find it obscure (e.g. executing the first paragraph, which
> defines 'RE', in reverse order).
>
> I know your goal wasn't to solve this little race scoring puzzle, but to
> use
> the puzzle as a means to learn J. So, if I get some more time over the
> week,
> I may select and dissect pieces of the code.
>
> In the meantime, it may be worth your while to play with it on your own. If
> you want to do that, it'll probably be easiest and most fruitful to break
> it
> into pieces and try them out, interactively, in the J session.
>
> So I recommend you replace all the local assignments (=.) with global
> assignments (=:), so all the intermediate names will be available to
> inspect
> and play with individually*.
>
> For example, I think you'll be interested in 'score' and 'catSumCount' (and
> their respective dependencies), because these are the heart of the problem
> and also highlight how J expresses such ideas differently, and perhaps more
> elegantly, than other programming languages:
>
> score 1+i. 3 NB. Fewer than 5 racers
> 0 0 0
> score 1+i. 5 NB. 5 racers
> 3 2 1 0 0
> score 1+i. 10 NB. 10 racers
> 3 2 1 0 0 0 0 0 0 0
> score 1+i. 11 NB. 11 racers
> 7 5 4 3 2 1 0 0 0 0 0
>
>
> pointGroup 1+i. 3 NB. Fewer than 5 racers
> 0
> pointGroup 1+i. 5 NB. 5 racers
> 3 2 1
> pointGroup 1+i. 10 NB. 10 racers
> 3 2 1
> pointGroup 1+i. 11 NB. 11 racers
> 7 5 4 3 2 1
>
>
> pointGroup
> (0;3 2 1;7 5 4 3 2 1;8 6 5 4 3 2 1;10 8 7 6 5 4 3 2 1) {::~ 4 10 20
> 49 I. #
>
>
> catSumCount 8 7 10 0 3 0 0 0 1 NB. 9 races, score=29, category=3
> +-+--+-+
> |3|29|9|
> +-+--+-+
> catSumCount 5 4 0 7 NB. 4 races, score=16, category=4
> +-+--+-+
> |4|16|4|
> +-+--+-+
> catSumCount 3000 NB. 1 race, score=super high, but still
> category=4
> +-+----+-+
> |4|3000|1|
> +-+----+-+
>
> catSumCount
> +/ (category ; ;) #
>
> (+/ category #) 8 7 10 0 3 0 0 0 1
> 3
>
> (+/ , #) 8 7 10 0 3 0 0 0 1
> 29 9
>
> 29 category 9 NB. x=sum of scores, y=# of races
> 3
> 35 category 7
> 1
> 35 category 2
> 1
> 33 category 5
> 2
>
> category
> 4 <. 1 + 35 30 20 I. (* 2&<:)
>
> It's worth noting the core parts of the scoring algorithm, 'pointGroup' and
> 'category', are both based on the dyad I. [1]. This is because those parts
> of the scoring system are defined in terms of ranges (a race of 5 to 10
> riders, a race of 11 to 20 riders vs. a total score from 0 to 20, a total
> score from 21 to 30, etc).
>
> The dyad I., interval index, is a sterling example of the expressivity and
> economy of J's notation. Here, it allows us to define these ranges by their
> essential characteristics, the demarcation lines between levels, rather
> than
> the (repetitive, superfluous) contents of each level. Not only is this
> convenient, but critically, it allows these essential characteristics stand
> out in our code, rendering it at once briefer and clearer. The
> fundamentals
> are immediately exposed.
>
> For example, compare 'category' with the original 'cat' or 'pointGroup'
> with
> the original 'points'. Heck, compare the code defining GROUPs to the table
> in the official scoring site you linked! Sometimes, formalizing a problem
> makes it even clearer than the specification. And, that little itch you
> feel to start playing with these rules, now that they're exposed and
> accessible?* That's what we mean when we say the notation is "suggestive".
>
> I hope this gives you a flavor of the benefits, and joys, of J.
>
> -Dan
>
> * And because it's really easy to do, given J's short feedback loop and
> interactive nature.
>
> [1] Definition of the dyad I., "Interval Index"
> http://www.jsoftware.com/help/dictionary/dicapdot.htm
>
>
>
> ----------------------------------------------------------------------
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>
--
Regards,
Alexander.
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