Rob Dixon wrote:
>
> John W. Krahn wrote:
>>
>> Rob Dixon wrote:
>>>
>>> John W. Krahn wrote:
perldoc -f print
print FILEHANDLE LIST
print LIST
print Prints a string or a list of strings. Returns true if
successful. FILEHANDLE may be a scalar variable name, in which
case the variable contains the name of or a reference to the
filehandle, thus introducing one level of indirection.
If the comma is missing then the first scalar or bareword argument is
treated as a filehandle.
>>>
Hmm. Well if I was wrong I'd like to be corrected, but it certainly
/looks/ and /behaves/ like indirect-object method call syntax, and the
equivalent arrow syntax works and does the same thing. But whether it's
really a method call under the hood I'm not absolutely certain,
especially when there are oddities like
print(STDOUT "text\n");
working fine. Whatever it is, it certainly stops being either a list
operator or a function call, so what else can it be?
So you are saying that everytime print() is used IO::Handle gets
sucked in somehow?
Well it's not so far-fetched. After all a lot of magical things happen in
Perl, and PerlIO does an on-demand load thing behind the scenes in 5.8. But
no, I know that print() is a built-in but thought that it was hooked in on
the back of a indirect object method call syntax. A couple of things support
this: first that
STDOUT->print()
works fine, and secondly that it's impossible to write a simple subroutine
prototype that does what print() and printf() do whereas that can be done for
all (?) other Perl functions. On the other hand you /can/ write an object
method that behaves the same syntactically.
And how would this have worked in Perl1 through Perl4 before OO was
added?
Now that is a puzzle and I hadn't thought of it. But it strikes me as an
astonishing choice to provide a unique syntax which is invalid for any other
built-in or user-written subroutine for just two built-in functions, and
solely to allow an optional first parameter. It is also a huge coincidence
that that same syntax pops up later on as a valid construct for object method
calls and so makes everything OK.
I am quite happy to believe you are right John, and if that is so then I
apologise to the list for my mistake, but am also left puzzling over what
seems to be a number of enigmas within a language I thought I knew well.
Sorry about the amount of quoting, but this goes back a few weeks and I thought
people may need a reminder.
I've just found a reference in the Perl documentation which says that things are
just as I thought they were, thank goodness!
perldoc perlobj
Indirect Object Syntax
The other way to invoke a method is by using the so-called "indirect
object" notation. This syntax was available in Perl 4 long before
objects were introduced, and is still used with filehandles like this:
print STDERR "help!!!\n";
But presumably it wasn't called 'indirect object notation' back then?
Rob
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