Re^2: Comma's and blocks

David,

Thanks for the response! The map and grep is a lot clearer (kind of).

#ex 1
map (sub {/dothis/},@_);
map {/and this/}, @_; #now doesnt compile

#ex 2
print STDOUT "hello";
print <STDOUT> , "Hello"; #runs
[download]

In the above example. The first line is making sense and opened my eyes to that for the map. As well the print uses a comma when a proper file handle '<' and '>' are used. Why do the use of proper terms affect the use of commas?

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Re^3: Comma's and blocks by erroneousBollock (Curate) on Oct 04, 2007 at 06:35 UTC
print <STDOUT> , "Hello"; #runs That doesn't do what you think. <STDOUT> reads from the STDOUT filehandle (which won't do anything useful). You can't put a comma between the file-handle and the printable content, the syntax is not short for any other syntax. `print HANDLE expression` is the normal form. `print expression` is parsed by perl to mean `print LATESTHANDLE expression` where LATESTHANDLE is the last handle given to `select()` (the default is STDOUT). -David	[reply] [d/l] [select]
Re^3: Comma's and blocks by mwah (Hermit) on Oct 04, 2007 at 09:41 UTC
zer: As well the print uses a comma when a proper file handle '<' and '>' are used. Why do the use of proper terms affect the use of commas As has been said in another response, the `print <STDOUT> , "Hello";` invokes reading a filehandle in list context and printing the result afterwards - but not through your "proper file handle" ;-) It has probably also been noted elswhere that this is like `print STDOUT <STDOUT>, "Hello";` The notation `print filehandle LIST` stems (IIRC) from the "indirect object notation", like `$q = new CGI;` #(no comma) which would, in "direct" object notation read: `$q = CGI->new()` From this point of view, the file example might be equivalent to `STDOUT->print("Hello");` #, which indeed is the case. The above idioms can be used in Perl after including the IO::Handle module, then it'll look like (pseudocode): `# from http://perldoc.perl.org/IO/Handle.html $io = new IO::Handle; # indirect object notation +! if ($io->fdopen(fileno(STDOUT),"w")) { $io->print("Hello"); # direct object notation! }` [download] See: IO::Handle documentation Regards mwa	[reply] [d/l] [select]


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