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Jon Willeke · Aug 9, 2017

For the most part, dynamic objects use local memory that is accounted for by $zstorage and $storage. However, some of it comes from other heap-allocated memory, similar to long strings. You can round trip a large JSON object through a dynamic object with %FromJSON()/%ToJSON(), even if an individual field exceeds the string limit. However, it is not currently possible to get the value of such a field within Caché.

Note that you should call %ToJSON() such that it outputs to a device or writes to a stream:

USER>d o.%ToJSON(stream)

USER>d o.%ToJSON()

Otherwise, you may get a STRINGSTACK error:

USER>w o.%ToJSON()

W o.%ToJSON()
^
<STRINGSTACK>
Jon Willeke · Mar 9, 2017

I don't really understand the question. It sounds like you're trying to convert from one eight-bit character set to another, but French generally uses the same character set as English, as far as I know. If you're using a Unicode instance of Caché, your first resort should be I/O translation: translate the input to Unicode, then translate on output to the desired character set. Doing it in COS is slower and less convenient.

That said, here are some things in your code that don't really make sense:

  1. a."i"; should probably be a.%Get(i).
  2. a-128; maybe a.%Get(c-128)?
  3. I don't understand the purpose of the first loop or the return statements.
  4. value(j); ...?

If I were to hazard a guess at rewriting this, my first try might be something like this:

for i=1:1:$l(str) {
    s c=$e(str,i)
    if $a(c)<128) {
        w c
    } else {
        w $c(a.%Get($a(c)-128))
    }
}
Jon Willeke · Jan 9, 2017

I'm not sure I understand the objection to %VID. I've seen a few different recommendations on how best to use it, but I think it does what you want in the following example:

select *
from (
    select top all *
    from Sample.Person
    order by DOB
) where %vid between 10 and 19

Regardless of the where or order by clause that you put in the sub-query, %VID refers to the position in the result set.

Jon Willeke · Jul 29, 2016

Greetings. Did you consult at InterSystems fifteen years ago? Long time no see.

My favorite technique to keep myself and others honest is to test with random inputs. This gives rise to two challenges: generating the input, and verifying the output. The input obviously depends on the problem: string, number, list, etc. When it comes to output, I look for invariants: x*y=(y*x), sort(x)=sort(shuffle(x)), etc. I sometimes even write another version of the code under test to act as an oracle that's perhaps slower, or not as general.

Caché has at least three ways to generate random numbers: $random(), $system.Encryption.GenCryptRand(), and the Basic Rnd() function.

$random(n) returns a number from 0 to n-1, where n'>1E17.

GenCryptRand(n) returns n bytes of cryptographically random data. You can convert it to a number using one of the $ascii() functions:

  • $a($system.Encryption.GenCryptRand(1))
  • $zwa($system.Encryption.GenCryptRand(2))
  • $zla($system.Encryption.GenCryptRand(4))
  • $zqa($system.Encryption.GenCryptRand(8)) - may be negative

Rnd() is interesting for a tester, because you can seed it with Randomize. If you don't use a seeded PRNG, you'll want to log your inputs somehow. It's frustrating to find a one in a billion bug, but not be able to reproduce it.