Re^2: Return Value of List-Producing Elements in Scalar Context

> A "list producing expression used in scalar context" does not produce a list. It just produces a single value, which is the last element in the comma-delimited expression.

Maybe better phrased "a list-producing expression used in scalar context" will not produce an intermediate LIST which is then evaluated in scalar context, but a scalar is produced depending on the value.

  DB<102> scalar (a..d)
 => "1E0"

  DB<103> sub tst {a..d}

  DB<104> tst()
 => ("a", "b", "c", "d")

  DB<105> scalar tst()
 => "1E0"

  DB<106> scalar ("a", "b", "c", "d")
 => "d"

  DB<107> sub tst { @{[a..d]} }

  DB<108> scalar tst()
 => 4
[download]

I wonder if a listify operator could help avoiding bugs when changing the return expression of a sub.

Cheers Rolf

( addicted to the Perl Programming Language)

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Re^3: Return Value of List-Producing Elements in Scalar Context by AnomalousMonk (Archbishop) on Jul 28, 2013 at 15:21 UTC
I wonder if a `listify` operator could help avoiding bugs when changing the return expression of a sub. It might help (and indeed, I think Perl6 has the `list` operator — but don't quote me), but the context in which the `..` and `...` range/flip-flop operators act is usually pretty clear. scalar alone serves pretty well in this case and in general since it's very easy to induce list context, so easy that one almost gets the impression it's the default!	[reply] [d/l] [select]
Re^4: Return Value of List-Producing Elements in Scalar Context by LanX (Saint) on Jul 28, 2013 at 18:09 UTC
I was already bitten by a case where I wanted to return a list like `1,2,3` from a sub and replaced it with `1..3` which acted differently in scalar context. True I should have used `wantarray`, but one intuitively expect a constant behavior... (I had different code-branches which returned and I didn't want to duplicate `wantarray` checks for each branch.) FWIW, here a possible implementation of `listify`: Re^3: wantarray alternative Maybe something like `l_return` (always return list) and `a_return` (always return array) could help... Cheers Rolf ( addicted to the Perl Programming Language)	[reply] [d/l] [select]