220 33185 <a33d3e68-f629-4048-8716-418b5778d471@isocpp.org> article
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From: Ray Hamel <rayghamel@gmail.com>
Newsgroups: gmane.comp.lang.c++.isocpp.proposals
Subject: Re: [idea for proposal] Adding std::shift to <algorithm>
Date: Wed, 12 Jul 2017 10:10:39 -0700 (PDT)
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A couple additional comments about your sample implementation:

`n` should be `std::iterator_traits<BidirIt>::difference_type`, which is a 
signed type (usually `std::ptrdiff_t`), instead of `unsigned`.

Bidirectional iterators aren't required to implement `operator-`, so the 
second argument to `std::move_backward` should be `std::prev(last, n)` 
instead of `last - n`.

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<div dir=3D"ltr">A couple additional comments about your sample implementat=
ion:<div><br></div><div><font face=3D"arial, sans-serif">`</font><font face=
=3D"courier new, monospace">n</font><font face=3D"arial, sans-serif">`=C2=
=A0should be `</font><font face=3D"courier new, monospace">std::iterator_tr=
aits&lt;BidirIt&gt;::difference_type</font><span style=3D"font-family: aria=
l, sans-serif;">`, which is a signed type (usually `</span><font face=3D"co=
urier new, monospace">std::ptrdiff_t</font><span style=3D"font-family: aria=
l, sans-serif;">`), i</span><font face=3D"arial, sans-serif">nstead of `</f=
ont><font face=3D"courier new, monospace">unsigned</font><font face=3D"aria=
l, sans-serif">`</font><span style=3D"font-family: arial, sans-serif;">.</s=
pan></div><div><span style=3D"font-family: arial, sans-serif;"><br></span><=
/div><div><span style=3D"font-family: arial, sans-serif;">Bidirectional ite=
rators aren&#39;t required to implement `</span><font face=3D"courier new, =
monospace">operator-</font><span style=3D"font-family: arial, sans-serif;">=
`, so the second argument to `</span><font face=3D"courier new, monospace">=
std::move_backward</font><span style=3D"font-family: arial, sans-serif;">` =
should be `</span><font face=3D"courier new, monospace">std::prev(last, n)<=
/font><span style=3D"font-family: arial, sans-serif;">` instead of `</span>=
<font face=3D"courier new, monospace">last - n</font><span style=3D"font-fa=
mily: arial, sans-serif;">`.</span></div></div>

<p></p>

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