i'm sorry that nobody seems to understand my question. i don't care about whether you use braces or brackets or whatever to make lists and group lists together or even to extract elements of lists, my question was only about how to do pattern matching in J. the answers i've gotten are totally unintelligibe to me. perhaps that shows my ignorance of J (which i certainly am) but perhaps because the 'explanations' presume a familiarity with the language. but i learned how to do array processing by reading the * explanation in words* of the APL code in the article "Life, Nasty, Brutish and Short" by McDonnell and then i simply implemented the same operations in WL which is an array processing language (it also uses rule-based methods, pattern matching, anonymous or pure functions and other programming methodologies or paradigms (many of which i don't like such as procedural Do loops). Having taught WL for many years to both university students and professionals , i found it very easy to explain how WL works to non-programmers in very disparate different fields of science (and i developed and made freely available a note set on it) who then went on after just a few hours (< 7) of instruction to do useful things of interest to them with it. there are no such resources for J. Stokes' book "Learning J" is fine but it's 613 pages long and costs over $80 just to double-side copy and spiral bind it and it contains no practical 'real-life' examples of using the language to do anything substantial (in contrast to my 4 books on programming in WL (or as it was previously and incorrectly referred, Mathematica), 3 of which use WL to write computer simulation programs for well-known models used in physics, chemistry, biology, sociology and economics. this enabled scientists in many fields to learn the language in the best possible way - by seeing it applied to real problems in their own fields. There are no equivalent resources for learning J, perhaps becuase few users of J are academicians who have the time to do it. i would encourage J enthusiasts to develop such resources (e.g. Data Science is a rapidly emerging field with not only courses, but also degrees being developed and offered at many universities and and J seems like it would be well-suited for use in the field) unless they want to see J used only by a coterie of specialists in finance and such and eventually consigned to the heap of other discarded programming languages, as has been the sad fate of APL. people like arthur whitney are content to develop proprietary languages for commercial use but it's a shame to see good concise, function-style languages such J lost amongst the garbage (i don't refer to garbage collecting methods) of truly awful programming languages. ken iverson well understood that a programming language carries with it a way of thinking and that's the REAL value of using a particular language (not just to make money doing financial analysis in companies).. my apologies for getting on a soapbox about this but to use the phrase that was totally mangled by U.S. VP candidate Dan Quayle, "a programming language is a terrible thing to waste" and i hate to see happen to J what happened to APL. but since WL is widely used and once it is made into a stand alone inexpensive app (as was J), it will probably take over as the programming language of choice in many fields as it already has in the physical and mathematical sciences. anyway, thanks for trying to educate me about J but it takes more then just using ascii characters to make J more teachable than APL was. but perhaps roger and others working with J simply don't care about getting J accepted and adopted by a wider group. that's their choice but in the new era of computation by computer which is rapidly replacing calculation by mathematics, it's unfortunate. in the unforgettable words of Mae West "a hard man is good to find" - her sexy variant of "a good man is hard to find" LOL.
-- *"Those who would sacrifice freedom for security deserve neither." - Benjamin Franklin* *"I think that the very notion that equations are a good approach to describing the natural world is a little bizarre." - Stephen Wolfram* * * ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
