foreach loop on one line

halecommarachel has asked for the wisdom of the Perl Monks concerning the following question:

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Re: foreach loop on one line by Kenosis (Priest) on Dec 03, 2013 at 00:49 UTC
Is this not valid code? Very close, but no, it's not. You need a code block with that `foreach`, as it is: `do { print "$_ could not be restored!\n" unless ( exists $found{$_} ) +} foreach (@files);` [download] or (more commonly) `foreach (@files) { print "$_ could not be restored!\n" unless ( exists $found{$_} ); }` [download] or you could `exists $found{$_} or print "$_ could not be restored!\n" foreach @file +s;` [download] Why does this last one work? An (inclusive) `or` statement is true iff one of its disjuncts is true. If `exists $found{$_}` is true, there's no need to evaluate the 'expression' on the other side of the `or`, because the entire `or` statement is true. However, if `exists $found{$_}` is not true, then the other side of the `or` will be evaluated, viz., `print "$_ could not be restored!\n"`. Hope this helps!	[reply] [d/l] [select]
Re: foreach loop on one line by BrowserUk (Patriarch) on Dec 03, 2013 at 00:54 UTC
I'd code that this way: `exists $found{$_} or print "$_ could not be restored!\n" for @files;` [download] With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]
Re: foreach loop on one line by KurtZ (Friar) on Dec 03, 2013 at 01:20 UTC
unfortunately post-fix statements cant be nested w/o do-blocks. I'd suggest: `print "$_ could not be restored!\n" for grep { not exists $found{$_} } @files;` [download] or even `print map {"$_ could not be restored!\n" } grep { not exists $found{$_} } @files;` [download]	[reply] [d/l] [select]
Re: foreach loop on one line by toolic (Bishop) on Dec 03, 2013 at 00:50 UTC
perlsyn `foreach (@files) { print "$_ could not be restored!\n" unless exists $found{$_}; }` [download]	[reply] [d/l]
Re: foreach loop on one line by tobyink (Canon) on Dec 03, 2013 at 09:25 UTC
The very first line of the documentation for Statement Modifiers (i.e. the postfix forms of `if`, `unless`, `foreach`, `while`, etc) says: Any simple statement may optionally be followed by a SINGLE modifier, just before the terminating semicolon (or block ending). `use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name`	[reply] [d/l] [select]