What is consteval?
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Apparently, consteval is going to be a keyword in C++20. The cppreference page for it is currently blank. What is it going to be and how does it relate to constexpr?
c++ c++20
asked Nov 17 '18 at 1:13
KevinZKevinZ
1,2121219
|
show 1 more comment
Apparently, consteval is going to be a keyword in C++20. The cppreference page for it is currently blank. What is it going to be and how does it relate to constexpr?
c++ c++20
asked Nov 17 '18 at 1:13
KevinZKevinZ
1,2121219
"Apparently, consteval is going to be a keyword in C++20" - provide a link to support this assertion.
– Neil Butterworth
Nov 17 '18 at 1:17
3
@NeilButterworth The cppreference page I already linked to claims it to be.
– KevinZ
Nov 17 '18 at 1:19
decltype(std::declval<f()>)'ish but .. fun stuff.
– Ted Lyngmo
Nov 17 '18 at 1:20
4
Bah, you're quick. I'll write it up this weekend.
– T.C.
Nov 17 '18 at 1:29
7
@NeilButterworth: By that reasoning, nobody can even call it "C++20" or say that there will even be a next version of C++. It is not unreasonable to ask about upcoming features that have been approved in accord with WG21 procedures at the various meetings. Like the most recent one.
– Nicol Bolas
Nov 17 '18 at 1:36
|
show 1 more comment
Apparently, consteval is going to be a keyword in C++20. The cppreference page for it is currently blank. What is it going to be and how does it relate to constexpr?
c++ c++20
asked Nov 17 '18 at 1:13
KevinZKevinZ
1,2121219
Apparently, consteval is going to be a keyword in C++20. The cppreference page for it is currently blank. What is it going to be and how does it relate to constexpr?
c++ c++20
c++ c++20
asked Nov 17 '18 at 1:13
KevinZKevinZ
1,2121219
asked Nov 17 '18 at 1:13
KevinZKevinZ
1,2121219
asked Nov 17 '18 at 1:13
KevinZKevinZ
1,2121219
asked Nov 17 '18 at 1:13
KevinZKevinZ
1,2121219
asked Nov 17 '18 at 1:13
KevinZKevinZ
1,2121219
1,2121219
"Apparently, consteval is going to be a keyword in C++20" - provide a link to support this assertion.
– Neil Butterworth
Nov 17 '18 at 1:17
3
@NeilButterworth The cppreference page I already linked to claims it to be.
– KevinZ
Nov 17 '18 at 1:19
decltype(std::declval<f()>)'ish but .. fun stuff.
– Ted Lyngmo
Nov 17 '18 at 1:20
4
Bah, you're quick. I'll write it up this weekend.
– T.C.
Nov 17 '18 at 1:29
7
@NeilButterworth: By that reasoning, nobody can even call it "C++20" or say that there will even be a next version of C++. It is not unreasonable to ask about upcoming features that have been approved in accord with WG21 procedures at the various meetings. Like the most recent one.
– Nicol Bolas
Nov 17 '18 at 1:36
|
show 1 more comment
"Apparently, consteval is going to be a keyword in C++20" - provide a link to support this assertion.
– Neil Butterworth
Nov 17 '18 at 1:17
3
@NeilButterworth The cppreference page I already linked to claims it to be.
– KevinZ
Nov 17 '18 at 1:19
decltype(std::declval<f()>)'ish but .. fun stuff.
– Ted Lyngmo
Nov 17 '18 at 1:20
4
Bah, you're quick. I'll write it up this weekend.
– T.C.
Nov 17 '18 at 1:29
7
@NeilButterworth: By that reasoning, nobody can even call it "C++20" or say that there will even be a next version of C++. It is not unreasonable to ask about upcoming features that have been approved in accord with WG21 procedures at the various meetings. Like the most recent one.
– Nicol Bolas
Nov 17 '18 at 1:36
"Apparently, consteval is going to be a keyword in C++20" - provide a link to support this assertion.
– Neil Butterworth
Nov 17 '18 at 1:17
"Apparently, consteval is going to be a keyword in C++20" - provide a link to support this assertion.
– Neil Butterworth
Nov 17 '18 at 1:17
3
3
@NeilButterworth The cppreference page I already linked to claims it to be.
– KevinZ
Nov 17 '18 at 1:19
@NeilButterworth The cppreference page I already linked to claims it to be.
– KevinZ
Nov 17 '18 at 1:19
decltype(std::declval<f()>)'ish but .. fun stuff.– Ted Lyngmo
Nov 17 '18 at 1:20
decltype(std::declval<f()>)'ish but .. fun stuff.– Ted Lyngmo
Nov 17 '18 at 1:20
4
4
Bah, you're quick. I'll write it up this weekend.
– T.C.
Nov 17 '18 at 1:29
Bah, you're quick. I'll write it up this weekend.
– T.C.
Nov 17 '18 at 1:29
7
7
@NeilButterworth: By that reasoning, nobody can even call it "C++20" or say that there will even be a next version of C++. It is not unreasonable to ask about upcoming features that have been approved in accord with WG21 procedures at the various meetings. Like the most recent one.
– Nicol Bolas
Nov 17 '18 at 1:36
@NeilButterworth: By that reasoning, nobody can even call it "C++20" or say that there will even be a next version of C++. It is not unreasonable to ask about upcoming features that have been approved in accord with WG21 procedures at the various meetings. Like the most recent one.
– Nicol Bolas
Nov 17 '18 at 1:36
|
show 1 more comment
1 Answer
1
active
oldest
votes
It declares immediate functions, that is, functions that must be evaluated at compile time to produce a constant. (It used to be spelled constexpr! in a previous revision of the paper.) In contrast, constexpr functions may be evaluated at compile time or run time, and need not produce a constant in all cases.
The adopted paper is P1073R3, which is not yet publicly available, but a previous revision is available and the introductory (motivation and high-level description) portion is about the same (except that the "Source Locations" section is deleted in R3).
edited Nov 17 '18 at 10:02
Rakete1111
35.8k1086123
answered Nov 17 '18 at 1:28
T.C.T.C.
108k14222331
Can we overload based onconsteval-ness?
– geza
Nov 17 '18 at 10:15
1
No, you can't, just likeconstexpr.
– T.C.
Nov 18 '18 at 6:21
1
It might be worth pointing out that the motivation is to have functions that rely on compiler data structures that need not be preserved in the binary.
– Davis Herring
Dec 24 '18 at 21:08
@geza You don't need to, but instead of overloading you can test an expression on compile-timeness by usage eithernoexceptoperator (formsvcorgcc) or through the__builtin_constant_poperator (forclangorgcc). Read these for details: * stackoverflow.com/questions/13299394/… * reddit.com/r/cpp/comments/7c208c/…
– Andry
Jan 28 at 15:07
@Andry: I don't think that these are 100% suited for the task.noexcepthas its problems, as far as I remember. And__builtin_constant_pis not usable with gcc, as its output depends on optimization level.
– geza
Jan 28 at 15:35
|
show 5 more comments
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
It declares immediate functions, that is, functions that must be evaluated at compile time to produce a constant. (It used to be spelled constexpr! in a previous revision of the paper.) In contrast, constexpr functions may be evaluated at compile time or run time, and need not produce a constant in all cases.
The adopted paper is P1073R3, which is not yet publicly available, but a previous revision is available and the introductory (motivation and high-level description) portion is about the same (except that the "Source Locations" section is deleted in R3).
edited Nov 17 '18 at 10:02
Rakete1111
35.8k1086123
answered Nov 17 '18 at 1:28
T.C.T.C.
108k14222331
Can we overload based onconsteval-ness?
– geza
Nov 17 '18 at 10:15
1
No, you can't, just likeconstexpr.
– T.C.
Nov 18 '18 at 6:21
1
It might be worth pointing out that the motivation is to have functions that rely on compiler data structures that need not be preserved in the binary.
– Davis Herring
Dec 24 '18 at 21:08
@geza You don't need to, but instead of overloading you can test an expression on compile-timeness by usage eithernoexceptoperator (formsvcorgcc) or through the__builtin_constant_poperator (forclangorgcc). Read these for details: * stackoverflow.com/questions/13299394/… * reddit.com/r/cpp/comments/7c208c/…
– Andry
Jan 28 at 15:07
@Andry: I don't think that these are 100% suited for the task.noexcepthas its problems, as far as I remember. And__builtin_constant_pis not usable with gcc, as its output depends on optimization level.
– geza
Jan 28 at 15:35
|
show 5 more comments
It declares immediate functions, that is, functions that must be evaluated at compile time to produce a constant. (It used to be spelled constexpr! in a previous revision of the paper.) In contrast, constexpr functions may be evaluated at compile time or run time, and need not produce a constant in all cases.
The adopted paper is P1073R3, which is not yet publicly available, but a previous revision is available and the introductory (motivation and high-level description) portion is about the same (except that the "Source Locations" section is deleted in R3).
edited Nov 17 '18 at 10:02
Rakete1111
35.8k1086123
answered Nov 17 '18 at 1:28
T.C.T.C.
108k14222331
Can we overload based onconsteval-ness?
– geza
Nov 17 '18 at 10:15
1
No, you can't, just likeconstexpr.
– T.C.
Nov 18 '18 at 6:21
1
It might be worth pointing out that the motivation is to have functions that rely on compiler data structures that need not be preserved in the binary.
– Davis Herring
Dec 24 '18 at 21:08
@geza You don't need to, but instead of overloading you can test an expression on compile-timeness by usage eithernoexceptoperator (formsvcorgcc) or through the__builtin_constant_poperator (forclangorgcc). Read these for details: * stackoverflow.com/questions/13299394/… * reddit.com/r/cpp/comments/7c208c/…
– Andry
Jan 28 at 15:07
@Andry: I don't think that these are 100% suited for the task.noexcepthas its problems, as far as I remember. And__builtin_constant_pis not usable with gcc, as its output depends on optimization level.
– geza
Jan 28 at 15:35
|
show 5 more comments
It declares immediate functions, that is, functions that must be evaluated at compile time to produce a constant. (It used to be spelled constexpr! in a previous revision of the paper.) In contrast, constexpr functions may be evaluated at compile time or run time, and need not produce a constant in all cases.
The adopted paper is P1073R3, which is not yet publicly available, but a previous revision is available and the introductory (motivation and high-level description) portion is about the same (except that the "Source Locations" section is deleted in R3).
edited Nov 17 '18 at 10:02
Rakete1111
35.8k1086123
answered Nov 17 '18 at 1:28
T.C.T.C.
108k14222331
It declares immediate functions, that is, functions that must be evaluated at compile time to produce a constant. (It used to be spelled constexpr! in a previous revision of the paper.) In contrast, constexpr functions may be evaluated at compile time or run time, and need not produce a constant in all cases.
The adopted paper is P1073R3, which is not yet publicly available, but a previous revision is available and the introductory (motivation and high-level description) portion is about the same (except that the "Source Locations" section is deleted in R3).
edited Nov 17 '18 at 10:02
Rakete1111
35.8k1086123
answered Nov 17 '18 at 1:28
T.C.T.C.
108k14222331
edited Nov 17 '18 at 10:02
Rakete1111
35.8k1086123
edited Nov 17 '18 at 10:02
Rakete1111
35.8k1086123
edited Nov 17 '18 at 10:02
Rakete1111
35.8k1086123
35.8k1086123
answered Nov 17 '18 at 1:28
T.C.T.C.
108k14222331
answered Nov 17 '18 at 1:28
T.C.T.C.
108k14222331
answered Nov 17 '18 at 1:28
T.C.T.C.
108k14222331
108k14222331
Can we overload based onconsteval-ness?
– geza
Nov 17 '18 at 10:15
1
No, you can't, just likeconstexpr.
– T.C.
Nov 18 '18 at 6:21
1
It might be worth pointing out that the motivation is to have functions that rely on compiler data structures that need not be preserved in the binary.
– Davis Herring
Dec 24 '18 at 21:08
@geza You don't need to, but instead of overloading you can test an expression on compile-timeness by usage eithernoexceptoperator (formsvcorgcc) or through the__builtin_constant_poperator (forclangorgcc). Read these for details: * stackoverflow.com/questions/13299394/… * reddit.com/r/cpp/comments/7c208c/…
– Andry
Jan 28 at 15:07
@Andry: I don't think that these are 100% suited for the task.noexcepthas its problems, as far as I remember. And__builtin_constant_pis not usable with gcc, as its output depends on optimization level.
– geza
Jan 28 at 15:35
|
show 5 more comments
Can we overload based onconsteval-ness?
– geza
Nov 17 '18 at 10:15
1
No, you can't, just likeconstexpr.
– T.C.
Nov 18 '18 at 6:21
1
It might be worth pointing out that the motivation is to have functions that rely on compiler data structures that need not be preserved in the binary.
– Davis Herring
Dec 24 '18 at 21:08
@geza You don't need to, but instead of overloading you can test an expression on compile-timeness by usage eithernoexceptoperator (formsvcorgcc) or through the__builtin_constant_poperator (forclangorgcc). Read these for details: * stackoverflow.com/questions/13299394/… * reddit.com/r/cpp/comments/7c208c/…
– Andry
Jan 28 at 15:07
@Andry: I don't think that these are 100% suited for the task.noexcepthas its problems, as far as I remember. And__builtin_constant_pis not usable with gcc, as its output depends on optimization level.
– geza
Jan 28 at 15:35
Can we overload based on
consteval-ness?– geza
Nov 17 '18 at 10:15
Can we overload based on
consteval-ness?– geza
Nov 17 '18 at 10:15
1
1
No, you can't, just like
constexpr.– T.C.
Nov 18 '18 at 6:21
No, you can't, just like
constexpr.– T.C.
Nov 18 '18 at 6:21
1
1
It might be worth pointing out that the motivation is to have functions that rely on compiler data structures that need not be preserved in the binary.
– Davis Herring
Dec 24 '18 at 21:08
It might be worth pointing out that the motivation is to have functions that rely on compiler data structures that need not be preserved in the binary.
– Davis Herring
Dec 24 '18 at 21:08
@geza You don't need to, but instead of overloading you can test an expression on compile-timeness by usage either
noexcept operator (for msvc or gcc) or through the __builtin_constant_p operator (for clang or gcc). Read these for details: * stackoverflow.com/questions/13299394/… * reddit.com/r/cpp/comments/7c208c/…– Andry
Jan 28 at 15:07
@geza You don't need to, but instead of overloading you can test an expression on compile-timeness by usage either
noexcept operator (for msvc or gcc) or through the __builtin_constant_p operator (for clang or gcc). Read these for details: * stackoverflow.com/questions/13299394/… * reddit.com/r/cpp/comments/7c208c/…– Andry
Jan 28 at 15:07
@Andry: I don't think that these are 100% suited for the task.
noexcept has its problems, as far as I remember. And __builtin_constant_p is not usable with gcc, as its output depends on optimization level.– geza
Jan 28 at 15:35
@Andry: I don't think that these are 100% suited for the task.
noexcept has its problems, as far as I remember. And __builtin_constant_p is not usable with gcc, as its output depends on optimization level.– geza
Jan 28 at 15:35
|
show 5 more comments
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"Apparently, consteval is going to be a keyword in C++20" - provide a link to support this assertion.
– Neil Butterworth
Nov 17 '18 at 1:17
3
@NeilButterworth The cppreference page I already linked to claims it to be.
– KevinZ
Nov 17 '18 at 1:19
decltype(std::declval<f()>)'ish but .. fun stuff.– Ted Lyngmo
Nov 17 '18 at 1:20
4
Bah, you're quick. I'll write it up this weekend.
– T.C.
Nov 17 '18 at 1:29
7
@NeilButterworth: By that reasoning, nobody can even call it "C++20" or say that there will even be a next version of C++. It is not unreasonable to ask about upcoming features that have been approved in accord with WG21 procedures at the various meetings. Like the most recent one.
– Nicol Bolas
Nov 17 '18 at 1:36