On 13 Apr 2008, Oleg Kobchenko posted
<http://www.jsoftware.com/pipermail/programming/2008-April/010462.html>
the following tacit expression as the solution to a question I had:
NEW [`(i.&:(0&{"1)~)`] } MASTER
Essentially, this fills in missing rows of table "NEW" with rows from
table "MASTER" (or, expressed differently, overlay the table "MASTER"
with the table "NEW"). Additionally, an error message results if table
"NEW" contains a (first-column) key not in table "MASTER".
Tacit expressions (particularly as solutions to problems) seem to be
nearly second nature to many people in this forum. However, being still
a newbie when it comes to J programming, I don't completely understand
exactly what's happening in Oleg's tacit expression above. (I
understand a bit here and there--emphasis on "bit"--but, as a whole, it
eludes me in terms of where I'm at in my learning.) Can Oleg or
somebody else translate it into an equivalent dyadic verb containing a
multi-line explicit definition without using any tacit expressions?
(I'm not looking for a different way of accomplishing the same thing;
for comparative learning purposes, I'd really like an explicit version
of Oleg's tacit expression above.) This particular function is
extremely important for some of my applications, and I need to be able
to do some step-by-step tracking (for example, with smoutput) of what's
happening with some new and different data.
I would really appreciate this! Thanks in advance!
Harvey
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