220 29600 <4fd0a3a2-5f0f-4c58-9184-d23827a802d4@isocpp.org> article
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From: Nicol Bolas <jmckesson@gmail.com>
Newsgroups: gmane.comp.lang.c++.isocpp.proposals
Subject: Re: Re: Add a "tuple_slice" function in <tuple>
Date: Wed, 30 Nov 2016 14:40:20 -0800 (PST)
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On Wednesday, November 30, 2016 at 5:19:13 PM UTC-5, =CE=9D=CE=B9=CE=BA=CF=
=8C=CE=BB=CE=B1=CE=BF=CF=82 =CE=91=CE=B8=CE=B1=CE=BD=CE=B1=CF=83=CE=AF=CE=
=BF=CF=85=20
wrote:
>
> Please refer to the related material, the proposed function does not=20
> operate only on std::tuple. It works on any type/entity that is a valid=
=20
> argument to std::tuple_size and std::get (namely std::array and=20
> std::pair) - the reason why it's bound to produce "tuple slices" is=20
> described in section 3 "Design consideration". I'm by no means implying=
=20
> this is superior to generalized slicing, but merely more simple and not=
=20
> requiring a language extension (plus it feels like it plays well with=20
> the existing tuple toolkit - it doesn't need to introduce extra machinery=
)=20
>

But if we have a language feature like that, it can do what your=20
tuple-slice function does, plus plenty of other things. Like this:

std::make_tuple(some_func([I1:I2]product_type)...);

You can find ways to make that work with lambdas, function calls, and=20
various other things. But it will never be as easily understandable and=20
easy-to-use as that. Better to go for the language feature, so that tuple=
=20
manipulation can be used by novices, rather than reserving it for complex=
=20
metaprogramming libraries.

--=20
You received this message because you are subscribed to the Google Groups "=
ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e=
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g.

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<div dir=3D"ltr">On Wednesday, November 30, 2016 at 5:19:13 PM UTC-5, =CE=
=9D=CE=B9=CE=BA=CF=8C=CE=BB=CE=B1=CE=BF=CF=82 =CE=91=CE=B8=CE=B1=CE=BD=CE=
=B1=CF=83=CE=AF=CE=BF=CF=85 wrote:<blockquote class=3D"gmail_quote" style=
=3D"margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: =
1ex;">Please refer to the related material, the proposed function does not=
=20
<br>operate only on std::tuple. It works on any type/entity that is a valid=
=20
<br>argument to std::tuple_size and std::get (namely std::array and=20
<br>std::pair) - the reason why it&#39;s bound to produce &quot;tuple slice=
s&quot; is=20
<br>described in section 3 &quot;Design consideration&quot;. I&#39;m by no =
means implying=20
<br>this is superior to generalized slicing, but merely more simple and not=
=20
<br>requiring a language extension (plus it feels like it plays well with=
=20
<br>the existing tuple toolkit - it doesn&#39;t need to introduce extra mac=
hinery)
<br></blockquote><div><br>But if we have a language feature like that, it c=
an do what your tuple-slice function does, plus plenty of other things. Lik=
e this:<br><br><div style=3D"background-color: rgb(250, 250, 250); border-c=
olor: rgb(187, 187, 187); border-style: solid; border-width: 1px; overflow-=
wrap: break-word;" class=3D"prettyprint"><code class=3D"prettyprint"><div c=
lass=3D"subprettyprint"><span style=3D"color: #000;" class=3D"styled-by-pre=
ttify">std</span><span style=3D"color: #660;" class=3D"styled-by-prettify">=
::</span><span style=3D"color: #000;" class=3D"styled-by-prettify">make_tup=
le</span><span style=3D"color: #660;" class=3D"styled-by-prettify">(</span>=
<span style=3D"color: #000;" class=3D"styled-by-prettify">some_func</span><=
span style=3D"color: #660;" class=3D"styled-by-prettify">([</span><span sty=
le=3D"color: #000;" class=3D"styled-by-prettify">I1</span><span style=3D"co=
lor: #660;" class=3D"styled-by-prettify">:</span><span style=3D"color: #000=
;" class=3D"styled-by-prettify">I2</span><span style=3D"color: #660;" class=
=3D"styled-by-prettify">]</span><span style=3D"color: #000;" class=3D"style=
d-by-prettify">product_type</span><span style=3D"color: #660;" class=3D"sty=
led-by-prettify">)...);</span></div></code></div><br>You can find ways to m=
ake that work with lambdas, function calls, and various other things. But i=
t will never be as easily understandable and easy-to-use as that. Better to=
 go for the language feature, so that tuple manipulation can be used by nov=
ices, rather than reserving it for complex metaprogramming libraries.<br></=
div></div>

<p></p>

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