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Re: Named Parameters

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December 16, 2019 12:04
Re: Named Parameters
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Dave Mitchell <> wrote:
:On Fri, Nov 29, 2019 at 04:44:24PM +0000, wrote:
:> Dave Mitchell <> wrote:
:> :Duplicate named arguments are allowed, the last value being used. This
:> :allows the useful idiom of foo(%defaults, %options) to work.
:> [...]
:> :Note that for duplicate arguments, only the right-most value is likely to
:> :evaluated; for example foo(name => $tied1, name => $tied2) would likely
:> :only call (tied $tied2)->FETCH(), although we don't guarantee this.
:> Such a guarantee would be useful for the foo(%defaults, %options) idiom.
:That's not obvious to me, Could you expand upon it?

%defaults could include values that are expensive to evaluate (eg via tie);
a guarantee that they would not be evaluated unnecessarily would make that
a reasonable thing to do. Failing such a guarantee one would probably choose
instead to write extra code at each calling site to check manually whether
the default is needed.

It's only a small benefit, not one worth moving the world for; but if once
we have an implementation it appears we could offer the guarantee with
no impact, it might be worth doing so.


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