Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Thu, 07 Jul 2005 18:23:15 -0500

Benjamin Franksen wrote:

What I proposed for the IVOA/IVOV example is easily adapted to other

scenarios, like simulation stuff, or alarm limit handling. Ok, all this

needs a developer who writes the code and (more importantly) designs an

appropriate interface that is general enough to be used in any record

type that needs such a facility.

I think you persuaded me about that, although I think I might simplify

your syntax a little (and forget what I said earlier about separating

class and struct). How about this DBD syntax:

struct (drvLimits, ValType) {
    field(high, ValType)
    field(low, ValType)
    method("STATUS constrain(ValType &value)")
}

The presence of one or more ValType arguments after the struct name

causes a template struct definition to be generated (without it, we just

get a regular struct definition):

template <typename ValType>
struct drvLimits {
    ValType high;
    ValType low;
    STATUS constrain(ValType &value);
}

The implementation of the drvLimits::constrain() method has to be

provided externally, just as with your code

OTOH, it would of course be great if we could assemble all these pieces

at record load time, rather than compile it into the record type, so

that each record will only have what it really uses. I just can't see

how to do this in a manner that is at the same time efficient and safe.

Well, apart from developing yet another programming language for the

task.

Unfortunately that's probably what we'd have to do, so I'm not trying to

think that one out any more.

- Andrew
--
Podiabombastic: The tendency to shoot oneself in the foot.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System