The answer to your original question is that no, J does not employ pattern matching in the sense it is used in WL.
The problem with your question, and the reason many of the answers to it are a bit confused, is that pattern matching is not a task--it is a syntactic (and low-level semantic) language choice. Your questions treat pattern matching as if it is a feature, and ask if J has this feature. It's cartainly possible to translate WL code using pattern matching to J at little cost in complexity, J simply does not use pattern matching to accomplish the same task. It's a bit like asking how to do pointer arithmetic in WL: WL does not use pointer arithmetic, but it doesn't need to. Marshall On Wed, Oct 09, 2013 at 07:42:26AM -0500, Richard Gaylord wrote: > 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
