Re: Feature Patch: Use completion to view parameter values

[Daniel Shahaf <d.s@xxxxxxxxxxxxxxxxxx>]

Bart Schaefer wrote on Mon, Mar 29, 2021 at 10:20:08 -0700:
> On Mon, Mar 29, 2021 at 10:11 AM Daniel Shahaf <d.s@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > I think that's right.  -workers@: Is it possible for a non-PM_SPECIAL
> > parameter have a custom getfn?
> 
> Only with the zsh/param/private module, I think, and in that case the
> getfn is just a wrapper around the default and doesn't add any
> side-effects.

Thanks, Bart.

And as to $AUTOINCREMENT, this isn't the first time I mentioned it as
a hypothetical, so I'm going to go ahead and post it here.  I suspect
people from the future will use this for something-or-other.

Works as you'd expect:
.
    % echo $AUTOINCREMENT $AUTOINCREMENT
    0 1
    % 

And in Marlon's patch with the ${(t)…*special*} exclusion bypassed:
.
    % zstyle \* extra-verbose yes
    % AUTOFOO=42
    % echo $AUTO<TAB><TAB>
    AUTOFOO       -- 42  AUTOINCREMENT -- 2
    AUTOFOO       -- 42  AUTOINCREMENT -- 4

Yes, it does actually increment the variable twice, probably because the
_parameters patch uses both ${(t)${(P)}} and then ${(P)}, and the former
does an increment too:
.
    % echo $AUTOINCREMENT ${(tP)AUTOINCREMENT} $AUTOINCREMENT 
    0 array-special 2
    %

I'm not proposing to commit $AUTOINCREMENT.

Cheers,

Daniel

P.S.  Another similar example is Perl's magic flip-flop variable:
«perl -E 'say --$| for (1..10)'»


diff --git a/Src/Modules/parameter.c b/Src/Modules/parameter.c
index ef9148d7b..179ac068e 100644
--- a/Src/Modules/parameter.c
+++ b/Src/Modules/parameter.c
@@ -2136,6 +2136,24 @@ scanpmusergroups(UNUSED(HashTable ht), ScanFunc func, int flags)
 }
 
 
+/* Functions for the AUTOINCREMENT special parameter. */
+
+static zlong autoincrement = 0;
+
+static zlong
+autoincrementgetfn(UNUSED(Param pm))
+{
+    return autoincrement++;
+}
+
+static void
+autoincrementsetfn(UNUSED(Param pm), zlong value)
+{
+    autoincrement = value;
+}
+
+
+
 /* Table for defined parameters. */
 
 struct pardef {
@@ -2192,8 +2210,13 @@ static const struct gsu_array dirs_gsu =
 static const struct gsu_array historywords_gsu =
 { histwgetfn, arrsetfn, stdunsetfn };
 
+static const struct gsu_integer autoincrement_gsu =
+{ autoincrementgetfn, autoincrementsetfn, stdunsetfn };
+
 /* Make sure to update autofeatures in parameter.mdd if necessary */
 static struct paramdef partab[] = {
+    SPECIALPMDEF("AUTOINCREMENT", PM_SPECIAL | PM_INTEGER,
+	    &autoincrement_gsu, NULL, NULL),
     SPECIALPMDEF("aliases", 0,
 	    &pmraliases_gsu, getpmralias, scanpmraliases),
     SPECIALPMDEF("builtins", PM_READONLY_SPECIAL, NULL, getpmbuiltin, scanpmbuiltins),
diff --git a/Src/Modules/parameter.mdd b/Src/Modules/parameter.mdd
index f71c17a72..b8fb93d54 100644
--- a/Src/Modules/parameter.mdd
+++ b/Src/Modules/parameter.mdd
@@ -2,6 +2,6 @@ name=zsh/parameter
 link=either
 load=yes
 
-autofeatures="p:parameters p:commands p:functions p:dis_functions p:functions_source p:dis_functions_source p:funcfiletrace p:funcsourcetrace p:funcstack p:functrace p:builtins p:dis_builtins p:reswords p:dis_reswords p:patchars p:dis_patchars p:options p:modules p:dirstack p:history p:historywords p:jobtexts p:jobdirs p:jobstates p:nameddirs p:userdirs p:usergroups p:aliases p:dis_aliases p:galiases p:dis_galiases p:saliases p:dis_saliases"
+autofeatures="p:parameters p:commands p:functions p:dis_functions p:functions_source p:dis_functions_source p:funcfiletrace p:funcsourcetrace p:funcstack p:functrace p:builtins p:dis_builtins p:reswords p:dis_reswords p:patchars p:dis_patchars p:options p:modules p:dirstack p:history p:historywords p:jobtexts p:jobdirs p:jobstates p:nameddirs p:userdirs p:usergroups p:aliases p:dis_aliases p:galiases p:dis_galiases p:saliases p:dis_saliases p:AUTOINCREMENT"
 
 objects="parameter.o"