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Re: Pre-RFC: builtin:: functions for detecting numbers vs strings

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February 23, 2022 23:42
Re: Pre-RFC: builtin:: functions for detecting numbers vs strings
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Karl Williamson <> wrote:
:On 2/23/22 15:03, Graham Knop wrote:
:> After the merge of, it is
:> possible to reliably distinguish between values that started as
:> numbers vs values that started as strings. Essentially, if the POK
:> flag is set, the value started as a string. If the POK flag is not set
:> and IOK or NOK is set, it started as a number. These flags can be
:> checked in XS, or via the B module, but cannot currently be checked in
:> pure perl. For serializers, being able to detect the original type of
:> a value is essential, so it would help to provide functions to provide
:> this information. For example, providing builtin::isnumber and
:> builtin::isstring, to go along with builtin::isbool.
:> This does potentially have a huge impact on the language as a whole.
:> While this is needed for serializers, providing easy access to this
:> type data will pretty much inevitably result in people using the
:> functions within perl for things like parameter validation. The values
:> "2" and 2 are meant to be fully interchangeable inside perl, and new
:> code distinguishing them will break many expectations.
:> Even with caveats, I do think this is something that the language
:> should provide. I am uncertain on the naming of the functions.
:> builtin::isnumber and builtin::isstring are perhaps the most
:> obvious, but they also imply that distinguishing these types is a
:> normal thing to do. We may want the function names to be more
:> opinionated, implying more strongly that they are meant to be used for
:> things like serialization, not internal type checking. That feels like
:> a losing battle though once any function of this type is available.
:What pops into my head is making them longer to type with sewn doubt:
:for example

Heh, my first thought was to call it "was_number" instead. Just enough
to imply origin rather than something intrinsic and permanent.


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