Associative Arrays: how to detect undefined?

[diskonext]

I love associative arrays, but in ChucK I foresee having the following problem:

[renderful]

This works:

[Antimon]

Also, arrays of non-primitives will return null if using an index that doesn't reference a set value (check the end of the associative arrays section in the manual here: http://chuck.cs.princeton.edu/doc/language/array.html#assoc), so if you feel the need to know if an index has been used or not, encapsulate your value in a class.

/Stefan

[renderful]

array["key'] == 0 works as well

[diskonext]

Antimon: thank you, that would work - although I prefer not to encapsulate ints and floats for this reason alone

Renderful: not quite sure what you mean? You seem to underline the problem as I want to be able to distinguish between 0 (the value) and 0 (the undefined key) - but can not do that at the moment, unless I use Antimon's trick.

I would like to be able to throw an associative array at an instrument that has many control points (FiltAfreq, FiltAQ, OscBGain, OscBPhase &c) and leave values undefined if I don't want to change them:

I would then loop over all potential commands to find out which ones need changing - with the current mechanism I could either never use 0 as a value, or I would set many parameters to 0 if not specified in the 'command' array.

I personally think that the NULL behaviour should be used for associative arrays of all types - or have a command to check for the existence of the key.

[renderful]

Ah, I understand now.

[Antimon]

I'm not sure I agree that you should be able to get NULL from an int[] array - I feel that would go against the notion of a primitive variable which shouldn't be able to be NULL. It can be useful to have a default value of zero as well. However, I can definitely see a need to be able to retreive the set of used keys for an array so you could do something like this:

array.keys() @=> KeySet keys;

if (keys.contains("FiltAfreq")) {
array["FiltAfreq"] => filterA.freq;
}

Maybe this already exists somewhere, just not in the docs?

/Stefan

[diskonext]

Either that or a keys() function that exports an array of existing keys to be used in a for-loop.

I had some discussions here in the office and the consensus was that NULL (or any other special bit sequence indicating an undefined value) is not always a good method, especially for the native types.

[cbit]

I was looking for a way of iterating over the associative portion of an array who's keys are not known. But as I gather from this discussion, array objects don't currently provide a way of finding out what their associative keys are, that's a pity. (subscribes to thread).