Re^3: If you believe in Lists in Scalar Context, Clap your Hands

[chromatic]

in reply to Re^2: If you believe in Lists in Scalar Context, Clap your Hands
in thread If you believe in Lists in Scalar Context, Clap your Hands

Are there cases where something that's unambiguously a list (and not an array) returns anything else than the last item?

A regular expression match with the /g flag, in scalar context.

A map or grep expression in scalar context.

The empty list my $x = () = some_expression; construct, in scalar context.

split, chomp, ....

A bare hash. (Want to argue over what a list is? Is it multiple, comma-separated expressions or something that pushes one or more items onto the internal stack? I'm not sure lists even exist as a language-level construct in Perl 5.)

[moritz]

One could argue that built-ins like map and grep don't return a list in scalar context, but are context sensitives themselves, so they are not fit for explaining "a list in scalar context". Likewise a regex match with /g.

[chromatic]

Sure, but you can also argue that 1, 2, 3, isn't a list of values but a list of expressions. Is this a list:

my $x = ($y = 1), ($z = 2);

How about this?

s{\\}{\\\\}g, print

Or this?

foo => scalar param( 'foo' )

It's difficult to tell without seeing the context... which makes me wonder if lists do exist, or if we should talk about the value of expressions instead.

[jwkrahn]

chomp???   How did chomp get in there?   It never returns a list.

[massa]

when used with a list, it returns the total number of characters chomped... and not a list (so, you are right that there is no "list context" to it.

[chromatic]

my @x = chomp <DATA>;

Bingo, @x is gets a one-element list -- or at least, it's a list in list context and a scalar in scalar context. Tricky! Here's a mind-bender. What's this?

1, 2, 3

It could be a three-element list, in list context, or it could be a scalar and two void expressions (which get optimized away), in scalar context. In void context, it could be nothing.

Update: Reworded one sentence.

[jwkrahn]

So, then, scalar also returns a list in list context?   (BTW, @x is an array, not a one element list.)