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Re: Proposal: initial type annotation in SV

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Sébastien Aperghis-Tramoni
May 6, 2013 13:08
Re: Proposal: initial type annotation in SV
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Dave Mitchell wrote:

> On Sun, May 05, 2013 at 11:45:25PM +0200, Sébastien Aperghis-Tramoni wrote:
> > So, here is a proposal to try making this situation a bit better:
> > annotate the SV to record the initial (or canonical) type of the the
> > value, that is the type of the value that was last affected to the SV.
> But I don't think that necessarily solves the problem. Consider:
>     while (<DATA>) {
> 	chomp;
> 	my ($x,$y) = split / /, $_;
> 	my $z = sqrt($x*$x + $y*$y);
> 	... serialise $x, $y, $z;
>     }
>     __DATA__
>     0.123 1.234
>     ...
> should $x, $y be serialised as strings or floats? I think the desire of
> the programmer would be for them to be floats, but the canonical form is
> string. In other words, the initial type still doesn't necessarily DWIM,
> and its still up to the programmer to manually ensure the output is as
> desired.

split() returns strings, so $x and $y should be annotated as strings, and
therefore serialized as strings.

Note that I do not expect to magically fix things, that's be unreasonable,
and would certainly break things. I mostly want to annotate the SV enough
so modules like serializers have hints to behave correctly.

> Also I think you'll be hard pushed to find any spare bits in sv_flags to
> record this info.

Yes, as I discovered through quick experiments, I was a bit too optimistic.
But this wasn't a surprise, because I guess that if it had been that simple,
it would have been implemented years ago.

Sébastien Aperghis-Tramoni

Close the world, txEn eht nepO.

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