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Hello,

I recently encountered an algorithm where I needed to access the map's last
element, knowing the map was non-empty. But I found that there is no
straightforward way to access the last (or first) element of a map.

So as suggested by this process : https://isocpp.org/std/submit-a-proposal
I'd like to propose the following: add the front() and back() methods, with
const and non const versions, to std::(multi)map and std::(multi)set, to
return a (const-) reference to the last / first element(s).

Like with other containers implementing these methods, no guaranty would be
given when the container is empty.

What do you think?

Cheers,
Olivier

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<div dir=3D"ltr">Hello,<div><br></div><div>I recently encountered an algori=
thm where I needed to access the map&#39;s last element, knowing the map wa=
s non-empty. But I found that there is no straightforward way to access the=
 last (or first) element of a map.</div><div><br></div><div>So as suggested=
 by this process :=C2=A0https://isocpp.org/std/submit-a-proposal I&#39;d li=
ke to propose the following: add the front() and back() methods, with const=
 and non const versions, to std::(multi)map and std::(multi)set, to return =
a (const-) reference to the last / first element(s).</div><div><br></div><d=
iv>Like with other containers implementing these methods, no guaranty would=
 be given when the container is empty.</div><div><br></div><div>What do you=
 think?</div><div><br></div><div>Cheers,</div><div>Olivier</div><div><br></=
div></div>

<p></p>

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I would think first try benchmarking map and set using begin() and rbegin()=
 for having to access the first and last elements vs similar access with fr=
ont and back on vector as well as begin() and rbegin(). I think some implem=
entation of begin() and rbegin() are slower than front() and back(). I thin=
k that front() and back() can make more sense in map and set then in vector=
 because they would represent min and max key values.

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..org/d/msgid/std-proposals/78ed8565-b36c-475e-83a8-c542ab14341b%40isocpp.or=
g.

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