Oolite Bulletins

Ahruman wrote:

As the functionality is no longer present in SpiderMonkey, it’s not possible to provide a transition period. ==/!= will not work for distinct Oolite objects in the next release, and will stop working in nightlies soon (probably tonight) even before the upgrade is complete.

Svengali wrote:

Does it mean we can already test our OXPs in trunk? Or should we wait some days...?

Ahruman wrote:

The correct way to compare vectors is to check whether the distance between them is below some threshold value:

Code: Select all

var equal = v.squaredDistanceTo(u) < thresholdSquared;

There is no comparable metric for quaternions in the current scripting interface. If you’re comparing quaternions, tell me why.

Switeck wrote:

Will it break this?:

if (!system.isInterstellarSpace && !player.ship.docked && (player.ship.speed > 10*player.ship.maxSpeed || timeAccelerationFactor > 4.0) && !player.alertHostiles && system.shipsWithRole("station", player.ship, 150E3).length < 1 && system.shipsWithRole("station", player.ship, 1500E3).length > 0 && missionVariables.deep_space_pirate_kills < (30 + system.countShipsWithRole("pirate-cove")*20 - system.government*3 ) )
this.addPirate()

Ahruman wrote:

In particular, it is no longer possible for Oolite to customize the behaviour of the ==/!= operators to usefully compare different objects with the same values. Doing this in the first place was an abuse of the engine which didn’t comply with JavaScript language semantics. This primarily affects vectors and quaternions.

<snip>

==/!= will not work for distinct Oolite objects

Commander McLane wrote:

Switeck wrote:

Will it break this?:

if (!system.isInterstellarSpace && !player.ship.docked && (player.ship.speed > 10*player.ship.maxSpeed || timeAccelerationFactor > 4.0) && !player.alertHostiles && system.shipsWithRole("station", player.ship, 150E3).length < 1 && system.shipsWithRole("station", player.ship, 1500E3).length > 0 && missionVariables.deep_space_pirate_kills < (30 + system.countShipsWithRole("pirate-cove")*20 - system.government*3 ) )
this.addPirate()

Well, it seems to contain neither "==" nor "!=" (which are the only comparators explicitly mentioned). So I would guess the answer is no.

Commander McLane wrote:

I need some clarification here. Am I right in assuming that comparing vectors and quaternions with "==" and "!=" will no longer work (what about "===" and "!=="?), but something like "system.ID == 7" is still okay? Or not, because it's an Oolite object as well?

My confusion is with the exact meaning of "compare different objects" / "distinct Oolite objects".

var v = new Vector3D(1, 2, 3);
var u = v;
var w = new Vector3D(1, 2, 3);

v === u; // True, they refer to the same object.
v == u;  // True, an object is always equal to itself.
v === w; // False, they’re distinct objects.
v == w;  // Formerly true as a magic special case, now false.

Commander McLane wrote:

But we still can compare properties of objects to whatever we want, using "==" and "!=", like in the small example above.

var a = false;
var b = (0 == 1);

a === b;   // True

var a = 5;
var b = 2 + 3;

a === b;   // True

true.flavour = "strawberry";
true.flavour; // Warning: reference to undefined property true.flavour

var a = new Object;
var b = new Object;

a == b;    // False; the objects are structurally identical, but == doesn’t test this.
a === b;   // False

var c = a;
a == c;    // True
a === c;   // True

a.flavour = "banana"; // The objects are no longer structurally identical.

a.flavour; // "banana"
b.flavour; // undefined
c.flavour; // "banana" — a and c refer to the same object.

var strPrimitive = "foo";
var strObjA = new String(strPrimitive);
var strObjB = new String(strPrimitive);
var customObject = { toString: function() { return "foo"; } }

// === is false for all combinations.

strPrimitive == strObjA;      // True
strPrimitive == strObjB;      // True
strObjA == strObjB;           // False!
customObject == strPrimitive; // True!

Thargoid wrote:

One other small clarification request. Will the usage of == for vectors and quaternions now generate a script error in the logs/console, or just an "incorrect" result when compared to its past usage?

Eric Walch wrote:

Ahruman wrote:

The correct way to compare vectors is to check whether the distance between them is below some threshold value:

Code: Select all

var equal = v.squaredDistanceTo(u) < thresholdSquared;

There is no comparable metric for quaternions in the current scripting interface. If you’re comparing quaternions, tell me why.

I have compared quaternions for the player.ship to see if it did not change orientation for a certain time. Instead of that I could compare two vectors to achieve the same goal. e.g. vectorUp and vectorRight.