bug#41981: Reference Manual on Vtables: Missing Information on Permission "h"
dsm...@roadrunner.com writes: > Is is documented in the docstring: > > scheme@(guile-user)> ,d make-struct-layout In the reference manual, a description of make-struct-layout directly precedes the '(define* (make-vtable ..) ..)' example that cannot be understood without somehow grasping what is documented about "h" in the docstring of make-struct-layout. However, the description of make-struct-layout in the reference manual says: "FIELDS is as described under ‘make-vtable’ (*note Vtables::)". But that description lacks the information on "h". It may be a matter of opinion. But my opinion stronly is that descriptions about the behavior around permission "h" do should appear in the reference manual in two places: The description of make-vtable and the description of make-struct/no-tail. After glancing at libguile/struct.c, "w", "h", and the depreciated "r" seem in fact to be all possible permissions. I will prepare a patch after I finish getting a good overview of Guile.
bug#41981: Reference Manual on Vtables: Missing Information on Permission "h"
Is is documented in the docstring: scheme@(guile-user)> ,d make-struct-layout - Scheme Procedure: make-struct-layout fields Return a new structure layout object. FIELDS must be a string made up of pairs of characters strung together. The first character of each pair describes a field type, the second a field protection. Allowed types are 'p' for GC-protected Scheme data, 'u' for unprotected binary data. Allowed protections are 'w' for normal fields or 'h' for hidden fields. Hidden fields are writable, but they will not consume an initializer arg passed to `make-struct'. They are useful to add slots to a struct in a way that preserves backward-compatibility with existing calls to `make-struct', especially for derived vtables.
bug#41981: Reference Manual on Vtables: Missing Information on Permission "h"
I am on the current master branch. The standard-vtable-fields is "pwuhuhpwphuhuhuh" on my system and something similar in the Reference Manual. In particular, it contains the permission letter "h", but I find no explanation in the manual what that means. Section 6.6.18.1 (Vtables) just mentions: "It used to be that the second letter for each field was a permission code, such as ‘w’ for writable or ‘r’ for read-only." And that read-only has become depriciated. At the end of section 6.6.18.4 (Meta-Vtables) is an example: (define* (make-vtable fields #:optional printer) (make-struct/no-tail (make-struct-layout fields) printer)) Without information on "h", I was not able to make sense of the fact, that fields with permission "h" somehow seem to be skipped by make-struct/no-tail when processing the two init values. In particular, for some reason, the value of printer is put into field 3 of the new structure and not in field 1, almost certainly somehow because fields 1 and 2 have "h". "h" should be documented.
