Jobs - bad assumption. Having said that, I don't want to discourage entrepreneurs, looking forward to your startup.
Loops and resources. Henry is modest and I haven't seen any remarks indicating you have absorbed Henry's book - J for C Programmers https://www.jsoftware.com/help/jforc/contents.htm If not, you should. > On 2020Dec 8, at 12:49, emacstheviking <obji...@gmail.com> wrote: > > Yes Henry I know about those. > I have a reasonable understanding of it but I lack the flying time in > general solving real issues with J. > > I spent 45 minutes last night just absorbing the page on ranks, array, > k-cells and frames....it makes sense when you read it! > > I am never going to get a job working with J unless I start my own start-up > I guess. > Thanks. > Sean > > > On Tue, 8 Dec 2020 at 19:36, Henry Rich <henryhr...@gmail.com> wrote: > >> Do you know about NuVoc and the ancillary pages pointed to below the >> primitive table? There is a lot written about rank. >> >> Henry Rich >> >> On 12/8/2020 2:27 PM, emacstheviking wrote: >>> Hauke, >>> PERFECT! >>> >>> ,.psz &.> pqfname@(res&;)"0 i.ncols >>> ┌───────────────────┐ >>> │id │ >>> ├───────────────────┤ >>> │invoice_id │ >>> ├───────────────────┤ >>> │created │ >>> ├───────────────────┤ >>> │status │ >>> ├───────────────────┤ >>> │ce_survey_id │ >>> ├───────────────────┤ >>> │organisation_id │ >>> ├───────────────────┤ >>> │payment_provider_id│ >>> └───────────────────┘ >>> >>> I just have to go through it step at a time until I fully understand the >>> magic! I have a vague understanding of rank and shape and that you can >> use >>> "0 "1 etc which affects the frame/k-cell metrics but could you explain >> what >>> it is doing here please? >>> >>> Thanks >>> Sean >>> >>> >>> On Tue, 8 Dec 2020 at 17:15, Hauke Rehr <hauke.r...@uni-jena.de> wrote: >>> >>>> Did I miss something or didn’t anyone answer the looping question yet? >>>> >>>> Without knowing much about what the names involved are doing, >>>> I think it ought to be >>>> pqfname@(res&;)"0 i. ncols >>>> which will have the shape >>>> (shape of i. ncols)×(shape of whatever pqfname res;0 returns) >>>> >>>> Am 08.12.20 um 14:34 schrieb emacstheviking: >>>>> Apologies for the length of this email but my brain has thrown one >>>> again... >>>>> I am currently working on a wrapper for Postgres using libpq-fe. It's >>>>> working but in need of some higher level functions to make result sets >>>>> easier to work with and feel more J-like. >>>>> >>>>> Once the query is executed, all results have been stored in RAM by the >>>>> library (not my first choice!) and then a value is obtained like so >>>>> >>>>> pqgetvalue result_set;row;col >>>>> >>>>> I've seen the source code for the library and the above translate >>>> directly >>>>> into an array read; >>>>> >>>>> char * PQgetvalue(const PGresult *res, int tup_num, int field_num) >>>>> { >>>>> if (!check_tuple_field_number(res, tup_num, field_num)) >>>>> return NULL; >>>>> return res->tuples[tup_num][field_num].value; >>>>> } >>>>> >>>>> >>>>> *# mema and management.* >>>>> >>>>> My plan was to write a 'pgquery' verb that takes the connection handle >>>> and >>>>> a SQL query (details to be settled) and then creates and executes the >>>> query >>>>> and returns back a table of boxed strings. My first question then is >> how >>>> is >>>>> the memory managed? I know from the documentation that memf is the >>>> natural >>>>> (obverse?) way to release memory but I wanted to know what happens if I >>>>> allocate a string with mema then return it and assign it into a boxed >>>>> structure. I have an ffi helper I wrote, I call it psz: >>>>> >>>>> psz=: 3 : 'memr (>y),0,_1' >>>>> >>>>> If I assign the return value to a variable: >>>>> >>>>> name =. psz a-mem-address-of-a-C-String >>>>> >>>>> is the pointer aliased or can I now memf the original address and still >>>>> have a viable copy of the string later. I ask this because, for the >>>>> lifetime of the result set object, the internally allocated memory is >>>>> always around until a pqclear is executed. In this particular case I am >>>>> hopefully correct in thinking that my returned box list of strings is >>>>> stable up until that time. >>>>> >>>>> (In --this case-- I don't need to release anything as the library does >> it >>>>> but I wanted a general asnwer about what memr actually does) >>>>> >>>>> I am more interested in the general case of using 'memr' though; does >> it >>>>> allocate a copy or, as I suspect, is it merely re-typing the memory >>>> address >>>>> as a string, in the same manner that 'ic' can be used to process >> integers >>>>> and floats. Some insights would be appreciated. >>>>> >>>>> >>>>> *# looping* >>>>> >>>>> This brings me to how best to extract the data from the internal result >>>>> set? My basic flow so far is this: >>>>> >>>>> conn=. pqconnectdb<'dbname=foo' >>>>> res=.pqexec conn;'select * from some_table' >>>>> nrows=. pqtuples res >>>>> ncols=. pqfields res >>>>> >>>>> So I might have 7 rows and 12 columns per row. Obtaining the name of >> the >>>>> columns is done using the pqfname call. I've been playing around and >> the >>>>> basic loop I have is awful! >>>>> >>>>> pgtest =: 3 : 0 >>>>> nrows=. pqntuples y >>>>> ncols=. pqnfields y >>>>> NB. get the column names as the first row >>>>> for_j. i. ncols do. >>>>> c =. pqfname y;j >>>>> smoutput psz c >>>>> end. >>>>> '' >>>>> ) >>>>> >>>>> I know I can do this 'looplessly' but have so far failed. It's going to >>>> be >>>>> a combination of bonding and maybe a hook or something but as I say, >>>> total >>>>> quagmire at the moment! The thing I require to be looped is this: >>>>> >>>>> pqfname res;col. NB. where col is i. ncols >>>>> >>>>> My thought process was along the lines of, produce an array of res;i >>>> pairs >>>>> but that feels ugly, then I thought about and played with trying to >> just >>>>> pass the i. ncols list into a bonded call to ; but somehow got stuck... >>>>> >>>>> So..I am after some nice solutions to how best to iterate ncols to >> obtain >>>>> the initial row of column names and then extract each row of data from >>>> the >>>>> result set...I know this can be done very succinctly, I continue to >> work >>>> on >>>>> it... >>>>> >>>>> Loving the challenge of thinking so differently! >>>>> >>>>> Thanks all, >>>>> Sean >>>>> ---------------------------------------------------------------------- >>>>> For information about J forums see http://www.jsoftware.com/forums.htm >>>>> >>>> -- >>>> ---------------------- >>>> mail written using NEO >>>> neo-layout.org >>>> >>>> ---------------------------------------------------------------------- >>>> For information about J forums see http://www.jsoftware.com/forums.htm >>>> >>> ---------------------------------------------------------------------- >>> For information about J forums see http://www.jsoftware.com/forums.htm >> >> >> -- >> This email has been checked for viruses by AVG. >> https://www.avg.com >> >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm >> > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
