Re^2: How exactly does no work?

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Re^3: How exactly does no work? by ww (Archbishop) on Feb 16, 2012 at 11:40 UTC
Minimal reference to the docs -- say `perldoc -f no` -- would put you on the path to answers. See also, as the docs suggest, `use`.	[reply] [d/l] [select]
Re^4: How exactly does no work? by locked_user sundialsvc4 (Abbot) on Feb 16, 2012 at 13:49 UTC
Okay, let’s just cut to the chase here. `use` is somewhat of an “overloaded” construct in Perl. It can be employed to reference an outside module (`use foo;`), or as a pragma to request certain compile-time behavior (`use strict;`). When I typed in what you entered as a “one-liner,” I got various compilation errors (as I should have). There are several things quite wrong with the code ... undeclared variables, parentheses, and so forth. On my system it will not compile at all. If I add `my ($b, $d);` I get no output at all because of course everything is now `undef`. So I am just going to set that (non-)example completely aside. `no warnings;` like its brother `use warnings;`, is a compile-time directive. It instructs Perl to behave in different ways when compiling your source-code into its internal form for execution. One form countermands the other. I do not profess to know the whys and wherefores of these things because the one thing that I do know is how to use them correctly, which IMHO is: At the top of every Perl program that you write, `use strict; use warnings;`. In the extremely rare case where you are forced to do something that these declarations would prevent, and you cannot find another way (translation: you haven’t looked hard enough yet, e.g. at UNIVERSAL), then you should bracket the smallest portion of code necessary. Insert `no warnings;`, then do the minimal amount of work, then immediately `use warnings;` again ... having first inserted a prodigious comment explaining exactly why you had to do this.
Re^5: How exactly does no work? by chromatic (Archbishop) on Feb 17, 2012 at 01:08 UTC
`use` is somewhat of an “overloaded” construct in Perl. It can be employed to reference an outside module (`use foo;`), or as a pragma to request certain compile-time behavior (`use strict;`). I think that explanation confuses more than it enlightens. In both cases (pragma and module), use does the same thing: `BEGIN { require 'Module.pm': 'Module'->import; };` [download] It always performs the require (modulo Perl's internal cache of what it's already loaded) and it always performs the import (modulo `use Foo ();`). use has no idea of whether what it's loading is a pragma. That part's up to the loaded thing's `import()` method.	[reply] [d/l] [select]
Re^4: How exactly does no work? by PerlOnTheWay (Monk) on Feb 16, 2012 at 11:43 UTC
`perldoc -f no` doesn't tell the answer.	[reply] [d/l]
Re^5: How exactly does no work? by ww (Archbishop) on Feb 16, 2012 at 11:51 UTC
Oh? For me, it provides the start I promised: C:\>perl -v This is perl 5, version 14, subversion 2 (v5.14.2) built for MSWin32-x +86-multi-thread (with 1 registered patch, see perl -V for more detail) .... Complete documentation for Perl, including FAQ lists, should be found +on this system using "man perl" or "perldoc perl". If you have access to + the Internet, point your browser at http://www.perl.org/, the Perl Home Pa +ge. C:\>perldoc -f no no MODULE VERSION LIST no MODULE VERSION no MODULE LIST no MODULE no VERSION See the "use" function, of which "no" is the opposite. C:\>perldoc -f use use Module VERSION LIST use Module VERSION use Module LIST use Module use VERSION Imports some semantics into the current package from the n +amed .... [download]	[reply] [d/l]
Re^5: How exactly does no work? by rovf (Priest) on Feb 16, 2012 at 13:58 UTC
Maybe a problem with your installation? What output do you get from `perldoc -f no`? -- Ronald Fischer <ynnor@mm.st>	[reply] [d/l] [select]
Re^5: How exactly does no work? by Anonymous Monk on Feb 17, 2012 at 00:39 UTC
`[doc://no]` no	[reply] [d/l]