220 30941 <08db6ce8-ca1c-4d75-a49a-d33e2fb8518b@isocpp.org> article
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From: Nicol Bolas <jmckesson@gmail.com>
Newsgroups: gmane.comp.lang.c++.isocpp.proposals
Subject: Re: compressed std::bitset<N>
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On Thursday, February 16, 2017 at 2:04:53 AM UTC-5, Vicente J. Botet 
Escriba wrote:
>
> Hi,
>
> I wanted to use bitset<8>, bitset<16>, bitset<32> to represent the mask 
> of 8,16 and 32 bits respectively but the sizeof them is 64 bits on the  
> systems I've tested.
>
> Wondering if others have suffered already of this situation. 
>
> How do you fill about adding a constraint on the implementation, so that 
> the sizeof shall be respectively 8, 16, 32 bits.
>

I feel the same way I would feel about adding constraints on 
implementations to be required to implement `std::uint32_t` et. al. That 
is, "not gonna happen".

The best you would reasonably get is requiring that a `bitset<N>` will have 
a size no bigger than a `uint_leastN_t`, if `N` is <= 64.

I don't see anything in `bitset`'s API that would make this non-workable. 
That doesn't mean there isn't, obviously.

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<div dir=3D"ltr"><br><br>On Thursday, February 16, 2017 at 2:04:53 AM UTC-5=
, Vicente J. Botet Escriba wrote:<blockquote class=3D"gmail_quote" style=3D=
"margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex=
;">
 =20

   =20
 =20
  <div bgcolor=3D"#FFFFFF" text=3D"#000000">
    <p><font size=3D"+1">Hi,</font></p>
    <p><font size=3D"+1">I wanted to use bitset&lt;8&gt;,</font><font size=
=3D"+1"> bitset&lt;16&gt;,</font><font size=3D"+1">
        bitset&lt;32&gt; to represent the mask of 8,16 and 32 bits
        respectively but the sizeof them is 64 bits on the=C2=A0 systems I&=
#39;ve
        tested.</font></p>
    <p><font size=3D"+1">Wondering if others have suffered already of this
        situation. <br>
      </font></p>
    <p><font size=3D"+1">How do you fill about adding a constraint on the
        implementation, so that the sizeof shall be respectively 8, 16,
        32 bits.</font></p></div></blockquote><div><br>I feel the same way =
I would feel about adding constraints on implementations to be required to =
implement `std::uint32_t` et. al. That is, &quot;not gonna happen&quot;.<br=
><br>The best you would reasonably get is requiring that a `bitset&lt;N&gt;=
` will have a size no bigger than a `uint_leastN_t`, if `N` is &lt;=3D 64.<=
br><br>I don&#39;t see anything in `bitset`&#39;s API that would make this =
non-workable. That doesn&#39;t mean there isn&#39;t, obviously.<br></div></=
div>

<p></p>

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