stable? (object -- isStable)

Inputs

• object: Current stack object whose stability is tested.

Outputs

• isStable: Known Cond result that is TRUE when the current stack object is stable.

This predicate follows the referenced target for known non-NIL Ref objects. It is the exact opposite of isDirty. Compile-time knownness and unknownness do not by themselves determine the result.

Behavior

• A fully known or forgotten-contents In-place object reports TRUE.
• A known non-NIL Ref object reports the current stability of its referenced target. This follows target stability, not target knownness.
• Known NIL Ref objects and unknown Ref objects report FALSE.
• Text objects report TRUE only when they are known and non-NIL.
• Code objects are tested by the current Code object itself, not by callability. User-visible creation paths such as codeRef and block assignment to Code still report FALSE.
• Meta objects report TRUE.

Example

{} 0 {} [
  value: 7;
  unknownValue: 0 dynamic;
  unknownText: 0 ("") dynamic @; # an unknown Text
  codeLocal: {} () {} codeRef;
  [] !codeLocal # a non-NIL Code

  "-- current stability versus forgotten-contents stability --" printCompilerMessage
  7 known? printStack _:;
  7 stable? printStack _:;
  7 unknownStable? printStack _:;
  7 isDynamic printStack _:;
  unknownValue known? printStack _:;
  unknownValue stable? printStack _:;
  unknownValue unknownStable? printStack _:;
  unknownValue isDynamic printStack _:;

  "-- references --" printCompilerMessage
  @value stable? printStack _:;
  @value unknownStable? printStack _:;
  @value isDynamic printStack _:;
  @unknownValue stable? printStack _:;
  @unknownValue unknownStable? printStack _:;
  @unknownValue isDynamic printStack _:;
  0nx value addressToReference stable? printStack _:; # a NIL Ref
  0nx value addressToReference unknownStable? printStack _:;
  0nx value addressToReference isDynamic printStack _:;

  "-- text, code, meta --" printCompilerMessage
  "hi" stable? printStack _:;
  "hi" unknownStable? printStack _:;
  "hi" isDynamic printStack _:;
  unknownText stable? printStack _:;
  unknownText unknownStable? printStack _:;
  unknownText isDynamic printStack _:;
  {} () {} codeRef stable? printStack _:;
  {} () {} codeRef unknownStable? printStack _:;
  {} () {} codeRef isDynamic printStack _:;
  @codeLocal stable? printStack _:;
  () stable? printStack _:;
  () unknownStable? printStack _:;
  () isDynamic printStack _:;

  0
] "main" exportFunction

Expected Output During Compilation

-- current stability versus forgotten-contents stability --
TRUE
TRUE
FALSE
FALSE
FALSE
TRUE
TRUE
TRUE
-- references --
TRUE
FALSE
FALSE
TRUE
TRUE
TRUE
FALSE
FALSE
FALSE
-- text, code, meta --
TRUE
FALSE
FALSE
FALSE
FALSE
FALSE
FALSE
FALSE
FALSE
FALSE
TRUE
FALSE
FALSE

See also

• dynamic builtin (object -- dynamicValue) Current stack-object forgotten-contents conversion.
• isDirty builtin (object -- isDirty) Current stack-object instability predicate; exact opposite of stable?.
• isDynamic builtin (object -- isDynamic) Current stable-and-unknown predicate; same predicate as unknownStable?.
• isStatic builtin (object -- isKnown) Historical name of the same current stack-object knownness predicate.
• known? builtin (object -- isKnown) Preferred public name of the same current stack-object knownness predicate.
• unknownStable? builtin (object -- isUnknownStable) Current stable-and-unknown predicate; same predicate as isDynamic.