Re^2: Default import function

That's what use does.

Yes, according to the documentation for use, it calls the import function:

It is exactly equivalent to
BEGIN { require Module; Module->import( LIST ); }
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except that Module must be a bareword.

But how does use call a function that hasn’t been defined anywhere? Are you saying that use itself creates an import function for the target module? (And if so, what are the contents of that function?)

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^3: Default import function by choroba (Cardinal) on Oct 24, 2016 at 06:55 UTC
I haven't checked the source, but it seems so, don't you think? The created sub seems empty: `~ $ perl -lwe '{package My; sub x {}} $INC{"My.pm"}=1; eval "use My"; +use Data::Dumper; $Data::Dumper::Deparse = 1; print Dumper \&$_ for v +alues %{"My::"}' $VAR1 = sub { package My; }; $VAR1 = sub ;;` [download] ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l] [select]
Re^4: Default import function by Anonymous Monk on Oct 24, 2016 at 13:08 UTC
That makes sense, at least in retrospect. As was mentioned earlier, `use()` is equivalent to `require()` followed by `import()`. The minimum implementation is probably to have class `UNIVERSAL`, which all Perl classes inherit from, have an empty `import()`, which in fact it does. So, to go back to the original question, it appears the most useful answer is that your Perl class in fact gets an `import()` method from somewhere, but the default one, inherited from `UNIVERSAL`, does nothing, so presumably they felt no need to document it. It's not documented under `UNIVERSAL` either.	[reply] [d/l] [select]
Re^5: Default import function by salva (Canon) on Oct 24, 2016 at 13:23 UTC
It doesn't work as you think! An `import` method is defined in `UNIVERSAL.pm`, but that file is not loaded unless it is explicitly requested as `use UNIVERSAL;` which is very rare practice. So, how does Perl handle the `import` method in modules not defining it? It is a special case: `/* excerpt from gv.c in the perl source code / if (!gv) { if (strEQ(name,"import") \|\| strEQ(name,"unimport")) gv = MUTABLE_GV(&PL_sv_yes); else if (autoload) gv = gv_autoload_pvn( ostash, name, nend - name, GV_AUTOLOAD_ISMETHOD\|flags ); if (!gv && do_croak) { / Right now this is exclusively for the benefit of S_method_c +ommon in pp_hot.c */` [download] when in a method call the requested method can not be resolved, perl checks if it is actually `import` (or `unimport`) and in that case, the call is just ignored.	[reply] [d/l] [select]
Re^5: Default import function by choroba (Cardinal) on Oct 24, 2016 at 13:19 UTC
The empty `import` doesn't seem to be the one coming from UNIVERSAL: `# UNIVERSAL should not contain any extra subs/methods beyond those # that it exists to define. The existence of import() below is a histo +rical # accident that can't be fixed without breaking code. # Make sure that even though the import method is called, it doesn't d +o # anything unless called on UNIVERSAL. sub import { return unless $_[0] eq __PACKAGE__; return unless @_ > 1; require Carp; Carp::croak("UNIVERSAL does not export anything"); }` [download] ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l] [select]