localtime array slice problem

The perldoc on localtime tells that its results are "returned by the time function to a 9-element array ", but my attempts to do the following in ActivePerl return no results:

perl -e "print @{localtime}[1,3];"
[download]

I thought perhaps you couldn't force list context out of the return value from a function:

perl -e "sub m {return (1,2,3);} print @{&m}[0,1];" #fails
[download]

but

perl -e "sub m {@q=(1,2,3); return \@q;} print @{&m}[0,1];" #succeeds
[download]

Pardon my ignorance on all this. I am testing out stuff I am learning from Effective Perl Programming (this book rocks) on array slices.

Celebrate Intellectual Diversity

Comment on localtime array slice problem Select or Download Code
Re: localtime array slice problem by dchetlin (Friar) on Jan 11, 2001 at 20:33 UTC
The `@` as a dereferencing operator (as you are using it) expects a reference, and thus puts its argument in scalar context. The return value of localtime in scalar context is a scalar (a string, to be precise). You want localtime to be called in list context. What you're looking for is `(localtime)[1,3]`. This causes localtime to be called in list context, and then takes elements 1 and 3 from the resultant list. However, be extra careful with that syntax when using it with print -- `perl -e'print (localtime)[1,3]'` won't work because it's interpreted as calling print with the argument localtime. Try either enclosing the whole slice in an extra set of parens, or putting a `+' in front of the first paren. The reason your last example works is that you're return a single value from your subroutine, namely a reference to an array. `@{...}` dereferences that array, and then the slice grabs the elements you want from it. You could fix your first subroutine example similarly to the localtime fix. Finally, and I know this is just an example, be very careful about naming subroutines `m'. It can cause some painful ambiguity with the m operator. -dlc	[reply] [d/l] [select]
Re: localtime array slice problem by I0 (Priest) on Jan 11, 2001 at 20:35 UTC
`print @{[localtime]}[1,3];` or `print ((localtime)[1,3]);`	[reply] [d/l] [select]
Re: localtime array slice problem by ChOas (Curate) on Jan 11, 2001 at 20:36 UTC
`#!/usr/bin/perl -w use strict; my @List=(localtime)[1,3]; print @List;` [download] result: 3311 your code with 'use strict': `Ambiguous use of @{localtime} resolved to @localtime at ./tmp line 6. Global symbol "@localtime" requires explicit package name at ./tmp lin +e 6. Execution of ./tmp aborted due to compilation errors.` [download] Start with using strict... build from there, it will tell you when you are REALLY messing up GreetZ!, ChOas print "profeth still\n" if /bird\|devil/;	[reply] [d/l] [select]
Re: Re: localtime array slice problem by InfiniteSilence (Deacon) on Jan 12, 2001 at 00:32 UTC
Good point about trying new things out inside of a script with warnings and use strict on. In this case, since I already knew that localtime is a function, I was able to use the following to get right past both -w and use strict: `#!/usr/bin/perl -w use strict; print @{localtime()}[1,3]; 1;` [download] Running this as `perl -c ltimetest.pl` [download] checks out okay, but running it tells me that I "Can't use string ("Thu Jan 11.... as an ARRAY ref while in strict subs..." Quick question: Why did -c pass where running the script generates the uncaught exception?- Celebrate Intellectual Diversity	[reply] [d/l] [select]
Re: Re: Re: localtime array slice problem by chipmunk (Parson) on Jan 12, 2001 at 01:48 UTC
`Can't use string %s as %s ref while "strict refs" in use` is a runtime error. -c is only for catching compile-time errors. There are many, many errors that can occur when a script is running but don't prevent the script from compiling. Here's another example: `$x = 0; $y = 7 / $x;` [download]	[reply] [d/l] [select]


go ahead... be a heretic
	PerlMonks

localtime array slice problem

The best material for plates (tableware) is: