// Meta - a "minimal" approach to adding meta-level to Java objects
// (implementing the interface IMeta)

// We allocate one extra field for each Java object to make it
// reasoning-compatible (reasoning-compatible = extensible with
// fields of any name at runtime).
//
// We couldn't go for 0 extra fields (meta values must be linked
// directly from the object) and there are no half fields in
// Java... so there you go.
//
// Also, if you don't use any meta data, you are probably not
// reasoning about anything. The point of reasoning in JavaX is
// to attach information to objects directly used in the program.

// Possible information contained in the meta field:
//   Origin, destination, security level, sender, cost center,
//   purpose, list of reifications, ...

// So here it is. THE FIELD YOU HAVE BEEN WAITING FOR!

// [We also have IMeta to retrofit foreign classes (rare but
// probably useful).]

//////////////////////
// The "meta" field //
//////////////////////

// Generic meta value of any kind, but the typical case is it's a
// Map with extra field values for the object etc.
// "meta" is volatile to avoid synchronization; but you can also synchronize on
// _tempMetaMutex() which is usually the object itself. Collections
// and maps are exempt from using the collections's monitor as the meta
// mutex because their monitor tends to be held for long operations
// (e.g. cloneList). For those we use a substantially more complex
// algorithm using a weakMap. Probably overkill. I may reconsider.

volatile O meta;

// The meta field is not transient, thus by default it will be
// persisted like anything else unless you customize your object
// to suppress or modulate this.

// ...and the interface methods

public void _setMeta(O meta) { this.meta = meta; }
public O _getMeta() { ret meta; }

// MOST functions are implemented in IMeta (default implementations)

// Scaffolding convenience functions

bool scaffoldingEnabled aka scaffolding aka scaffolded() { ret main scaffoldingEnabled(this); }
bool scaffoldingEnabled(O o) { ret main scaffoldingEnabled(o); }

// Implementing setMetaToString

S toString_base() { ret super.toString(); }
toString {
  O o = metaGet toString(this);
  if (o cast S) ret o;
  if (o cast IF1) ret str(o.get(this));
  ret toString_base();
}

Began life as a copy of #1031838