On Wed, Nov 26, 2025 at 6:14 PM Lev Minkovsky via Std-Proposals
<std-proposals_at_[hidden]> wrote:
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> Hello all,
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> Thank you for your active participation in the discussion about extended precision types.
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> There is a better way to accomplish what I am looking for. Virtually every hardware architecture provides some support for double precision math. For example, 32-bit platforms can effectively and directly do 64-bit operations, and 64-bit platforms – 128-bit operations. A good deal of that support is already available in existing C++ implementations.
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> We now have the following set of integral types:
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> size-constrained fundamental types (e.g., long long is at least 64 bit).
> fixed-size library types, aliasing to fundamental types (e.g., int16_t)
> the potential future wide gamut of bit-precise types (e.g., _BitInt(48)).
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> In addition to those, we can introduce the following word-length-dependent types:
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> _Single. unsigned _Single
> _Mult2, unsigned _Mult2.
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> The _Single types will be aliases of some C++26 fundamental types. For example, on x64, _Single can be aliased to long long. The _Mult2 types on 32-bit platforms can aliased to (unsigned) long long, and on 64-bit platforms introduce standard 128-bit integer types.
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> If we want to, we can also have the respective literals. For example,
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> auto x = 1sl;
> auto y = 1m2;
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> Here, x will be a single precision integer, and y – double precision integer, both equal to 1.
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> All this should be easy to implement with native-level performance, and therefore we should expect quick and wide adoption.
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> Please let me know if you think this is proposal worthy.

It's unclear to me why someone would use these types. That is, what
code am I writing where I am 100% fine with an integer that's only
64-bits in size (ie: I don't need it to be bigger), but I would
specifically want it to be 128-bits on 64-bit platforms? If I just
needed at least 64-bits, I'd use `int_least64_t` or `long long` or
`_BitInt(64)`. So what am I doing where I want it to be 128-bits on
64-bit platforms?

What is the programmer thinking about when they use `_Multi`?

You also talked about "quick and wide adoption", as if that's a
primary goal of the proposal. I don't feel that a proposal should
exist primarily because it can be adopted quickly. That might be a
consideration, and certainly if people think that a proposal will be
ignored by meaningful compilers, that sounds like a problem with the
proposal. But it shouldn't be that important.