Formal comment #161 (defect)

Problems in description of instantiation semantics
Reported by: 	Andre van Tonder
Version:	5.92

Pages : 25-26 Dependencies: None

Summary:

Library instantiation semantics insufficient or incorrect.

Description:

The document does not distinguish evaluation times of macro
definitions and variable definitions. In particular, it states "An
instance of a library corresponds to an evaluation of its definitions
and expressions in a particular phase relative to another library."

Given this, the following statement is incorrect:

        "... if the expanded form of one library references at phase 0
        an identifier from another library, then before the
        referencing library is instantiated at phase n, the referenced
        library must be instantiated at phase n."

It is incorrect because it requires that macro definitions in the
referenced library must be re-evaluated (unnecessarily) when the
/already expanded/ referencing library is run.

Furthermore, the decription on pages 25-26 is incomplete. It does not
actually decribe the phase where the macro definitions in an imported
must be evaluated (but the variable definitions must not).


RESPONSE:

For the next draft, we have restored the concept of "visiting" a
library, and adjusted the text accordingly:

 * A new paragraph of "visiting" follows the existing one on
   "instantiating".

 * The last two paragraphs of 6.2 (not counting the rationale) have
   been extended to specify the lack of guarantees about the timing of
   visits.