compile-time-constant Questions
10
Related: Function returning constexpr does not compile
I feel like constexpr is limited in usefulness in C++11 because of the inability to define two functions that would otherwise have the same s...
Caruso asked 20/1, 2012 at 3:54
5
Solved
I have a user-defined literal operator that only makes sense for strings of a specific length, like this:
constexpr uint16_t operator "" _int(const char* s, std::size_t len)
{
return len == 2 ? s...
Klenk asked 29/11, 2017 at 1:22
2
Solved
Is there anyway I can tell function argument is compile time-constant or not in C++ 11?. I would like to branch the functions body based on the results. For example, like below;
template <T>
...
Burin asked 12/7, 2023 at 17:9
6
Solved
Is it possible to declare a constant Guid in C#?
I understand that I can declare a static readonly Guid, but is there a syntax that allows me to write const Guid?
Horticulture asked 7/2, 2011 at 21:5
1
Solved
The Raku docs describe ::?CLASS as a compile-time variable that answers "Which class am I in?". Then, a couple of paragraphs later, it mentions $?CLASS, and says that it answers "Whi...
Nidorf asked 23/2, 2022 at 18:5
2
Solved
Is the following code legitimate?
template <int N>
class foo {
public:
constexpr foo()
{
for (int i = 0; i < N; ++i) {
v_[i] = i;
}
}
private:
int v_[N];
};
constexpr foo<5>...
Leban asked 9/1, 2020 at 10:56
14
Solved
So, I am working on this class that has a few static constants:
public abstract class Foo {
...
public static final int BAR;
public static final int BAZ;
public static final int BAM;
...
}
...
Flinty asked 30/9, 2010 at 3:2
1
Solved
I have been trying to understand how static variables are initialized. And noted a contradiction about the order of constant initialization and zero initialization at cppref and enseignement.
At cp...
Unproductive asked 21/9, 2021 at 6:40
1
Solved
According to the documentation:
pub const unsafe extern "C" fn CMSG_SPACE(length: c_uint) -> c_uint
However, if I compile
fn main() {
let _ = [0u8; libc::CMSG_SPACE(1) as usize];
}
...
Refugia asked 8/9, 2021 at 19:55
3
Solved
I want to compute the factorial of a const:
const N: usize = 4;
const N_PERMUTATIONS = factorial(N);
The solutions I've thought of that don't work in Rust 1.18 are:
const fn — conditional stateme...
Snuck asked 9/6, 2017 at 2:45
0
Despite reading through some StackOverflow posts (this and this) and cppreference pages, I cannot figure out how a non-static constexpr local variable would be beneficial compared to a static const...
Woodham asked 9/7, 2020 at 19:11
8
Solved
The Java language documentation says:
If a primitive type or a string is defined as a constant and the value
is known at compile time, the compiler replaces the constant name
everywhere in the...
Tit asked 31/1, 2012 at 16:18
2
Solved
#include <iostream>
#include <cstdint>
using namespace std;
static_assert(-1 == numeric_limits<uint64_t>::max()); // ok
static_assert(-1 == numeric_limits<uint32_t>::max()...
Prudy asked 15/4, 2020 at 15:4
2
Solved
Can the ternary (conditional) operator be used as an analogous to constexpr if(), introduced in C++17?
I would like to add some conditionality to member variables initialization in a template. Woul...
Fibrilla asked 29/1, 2020 at 17:23
1
Solved
I have an annotation that requires defaultValue to be compile-time constant. I take defaultValue from enum below:
enum class RaceType {
MARATHON,
SPRINT;
companion object {
fun apply(type: Ra...
Impending asked 20/1, 2020 at 16:13
1
I want to implement atoi() function at compile time (in C++ language, by using C++11 or C++14 standard). So it should be able to parse text enclosed in double quotes as number, or repor an error. M...
Pyroconductivity asked 30/12, 2019 at 18:26
5
I have a code like
template <size_t N>
class A
{
template <size_t N>
someFunctions() {};
};
Now I want to create instances of the class and call the functions in it in a for loop ...
Mccalla asked 5/12, 2019 at 17:52
5
Solved
I have a Perl module that I have declared some constants:
use constant BASE_PATH => "/data/monitor/";
In live operation the constant will never change but I wish to be able to modify it in my...
Saucedo asked 1/7, 2009 at 15:28
1
Solved
I have a C library that expects string type that explicitly defines the string length:
#[repr(C)]
pub struct FFIStr {
len: usize,
data: *const u8,
}
Because this type is used as a static, I'd ...
Soldo asked 27/10, 2019 at 5:26
3
Solved
Is it possible to declare a new type (an empty struct , or a struct without an implementation) on the fly?
E.g.
constexpr auto make_new_type() -> ???;
using A = decltype(make_new_type());
usi...
Scrapple asked 25/3, 2019 at 16:1
1
Solved
#include <type_traits>
int main()
{
std::is_constructible_v<int&, const int&>; // false, as expected.
std::is_copy_constructible_v<int&>; // true, NOT as expected!
...
Woaded asked 1/2, 2019 at 7:19
2
Solved
I understood what a compile time constant rule is from Compile-time constants and variables.
declared as final
have a primitive or String type
initialized at the same time as the declaration
init...
Translatable asked 22/12, 2018 at 16:57
1
Solved
I would like to initialize a variable during compilation time. For example, I would like to initialize the variable VAR to VALUE when compiling the code:
match env::var("VAR") {
Ok(value...
Kaylil asked 31/7, 2018 at 19:32
3
Solved
I have the following code, where I get the error "PHP Fatal Error: Constant expression contains invalid operations". It works fine when I define the variable in the constructor. I am using La...
Wolfsbane asked 27/11, 2016 at 10:24
3
Solved
I want to prevent invalid value enum assignment. I know if i even assign value that is not in enum it will work. Example:
enum example_enum
{
ENUM_VAL0,
ENUM_VAL1,
ENUM_VAL2,
ENUM_VAL3
};
void...
Wohlen asked 27/9, 2016 at 12:58
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