Another problem domain, I have done a lot of work in connectivity matrices (yes
including transitive closure) in problem spaces such as;
Minimum Path
Credit Counterparty Limits in financial markets
I did this in kdb (another descendant of APL) but the technique may be directly
implemented in J also as a very nice Linear Algebra solution, reference is here;
https://code.kx.com/q/cookbook/lp/
The solution was a handful of lines of code, but I too come from an older APL
and C programming background and a scalar language approach would be a very
considerable and less robust task by comparison.
The technique is readily transcribed to J using functions very similar to what
Raul already provided in this thread mentioning work done by Roger also.
Rob Hodgkinson
> On 29 Nov 2017, at 2:23 pm, Don Kelly <[email protected]> wrote:
>
> While I have done, in the past, with APL*PlUS, (Yes, I am that old) more than
> I have done with J (interest rather than need is now dominant), I find that
> the potential of J to deal with many things in a compact way is superior to
> that APL and any other languages which I have dealt with -from MAD, Fortran,
> Basic, Pascal and C++ . In J, the problem solution is the main objective and
> the bit twiddling can be left to the idiot box, not the programmer. The array
> orientation eliminates much of the need for looping and control structures
> which, while defined, are often unneeded.
>
> An example is (explicit) scripts to solve electric and magnetic fields under
> power transmission lines. The scripts are compact and take advantage of the
> use of complex numbers for electrical as well as positional factors and
> geometric means -- there is no looping that would have to be explicitly
> built as would be the case in most languages. Explicit loops have their
> place and usefulness and this is recognized in J.
>
> The difference between J and most other languages is that J eliminates the
> housekeeping that the idiot box can do -so that the*problem rather than the
> housekeeping is dominant*. It is true that compiled C++ lies behind many of
> the operations - but J is beyond C++ as much as C++ is beyond assembly
> language for programming.
>
> Don Kelly
>
>
> On 2017-11-28 12:59 PM, Andrew Dabrowski wrote:
>> As much as I've complained about J in these forums I've been having a good
>> time translating some simple code into J. Someone gave me wise advice, to
>> stick with explicit definitions until I know the language well, which advice
>> I have cordially ignored because I'm having too much fun playing code golf
>> with tacit tangles.
>>
>> I was fascinated by J because it seemed to try to build on aspects of the
>> human linguistic system. Natural language unfolds in one dimension, time,
>> so everything relevant to understanding a particular word in a sentence
>> either came before it or is yet to come. J seemed to emulate this by having
>> verbs which relate directly only to objects on the immediate left and
>> immediate right. Moreover J seemed to be following a linguistic paradigm in
>> have nouns which are inert, verbs that act on nouns, and adverbs which
>> modify objects. This seemed like a promising way to exploit humans' natural
>> linguistic capabilities.
>>
>> But maybe that's not way the J community currently sees J. Do you love J
>> most because of (pick only one)
>>
>> 1. the NL inspired syntax;
>>
>> 2. the suite of array utilities;
>>
>> 3. the concision of J code;
>>
>> 4. its being open-source; or
>>
>> 5. _____________________?
>>
>> I've come to feel that all programming languages are ugly compromises that
>> are about equally good/bad at solving practical problems, and the "best"
>> language is just the one you know the best. I used to be contemptuous of
>> Perl, but after having learned it well enough for my purposes I now kind of
>> enjoy the brain teaser quality of trying to fit problems into its
>> procrustean bed (although I still think it's a silly language). I have no
>> doubt that I could live happily with J as my primary language, but only
>> after an extended period of being handcuffed to it and forced to assimilate
>> its quirks. I don't know that I'll have the patience for that.
>>
>> Is there any project in the J repos that demonstrates the strength of J, as
>> opposed to just showing that it's at least as good as other languages? Any
>> project that would have been significantly harder to complete with say
>> Python? Does J have any killer advantage, even in just one aspect of
>> programming? Or does J just appeal to you the way pistachio ice-cream
>> might, it just tickles your palate in a no-accounting-for-taste way? That's
>> how it appeals to me.
>>
>> I was hoping someone could talk me into studying J seriously, but now it
>> looks to me like a language which, with APL, has had enormous beneficial
>> influence on many other languages, but which has failed to learn in its turn
>> from them. J seems a tad solipsistic.
>>
>>
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
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