Template argument deduction is a compiler attempt to deduce template arguments when some are omitted.
Questions tagged [template-argument-deduction]
692 questions
6
votes
4 answers
disable template member function if return type is an array
https://www.godbolt.org/z/_4aqsF:
template struct Container
{
template T find_if(TPred pred); // the culprit
};
template Container MakeContainer(T const &)
{
return Container();
}
int…
peterchen
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6
votes
0 answers
Why must we specify template arguments for template base class when calling its constructor?
The following code snippet compiles only if I explicitly specify the template argument T for the Base struct in Derived ctor:
template
struct Base
{
Base(int) {}
};
template
struct Derived : Base
{
Derived(int i) :…
undermind
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6
votes
1 answer
Error when using operator << with implicitly converted non-fundamental data types
I have a struct that works as a wrapper for other types as follows:
template
struct A {
A& operator=(const T& value){
m_value = value;
return *this;
}
operator T() const {
return m_value;
}
private:
T…
dtell
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6
votes
1 answer
User-defined vs automatic template deduction guides priorities
Let's say we have a class like this with a user-defined deduction guide:
template
struct Foo
{
Foo(Args&&...) { std::cout << "just Args: " << __PRETTY_FUNCTION__ << std::endl; }
Foo(Args&&..., T&&) { std::cout…
0xd34df00d
- 1,496
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6
votes
0 answers
Deducing class template parameters from variadic value-initialization (clang vs g++)
Consider the following variadic class template:
template
struct foo
{
template
foo(Us...) { }
};
If I try to instantiate foo in the following way, both g++(trunk) and clang++(trunk) are happy:
auto o =…
Vittorio Romeo
- 90,666
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6
votes
1 answer
For a type Class::Type, can I derive const Class::Type from a const Class?
I am implementing a container like:
template
class Container
{
public:
using value_type = T;
...
};
Is there a good way to derive a const value_type from const Container?
Background:
I have implemented iterator types via a…
jamesdlin
- 81,374
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6
votes
2 answers
could not deduce template argument for T* from FieldType* (Visual C++ only)
This code compiles OK on g++ (Coliru), but not Visual C++ (rextester) - both online and my desktop.
It is a simplified version of a much larger Visual Studio 2015 project.
class AAA{
public: template static T* test(T* hqi){
…
javaLover
- 6,347
- 2
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- 67
6
votes
2 answers
template deduction: const reference and const pointer
template
void f(T t)
{}
int x = 1;
const int & rx = x;
const int * px = &x;
f(rx); // t is int
f(px); // t is const int *, instead of int *, WHY???
I'm confused now. According to Effective Modern c++,
It’s important to recognize that…
Yves
- 11,597
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6
votes
3 answers
Does C++11, 14 or 17 provide a way to get just the arguments out of a decltype()?
This question is very similar to: "Extract just the argument type list from decltype(someFunction)". I'm not sure the answers there work for what I'm intending though. I'd like to be able to create a template function that deduces the type of its…
Aaron Altman
- 1,705
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6
votes
2 answers
C++ template parameter deduction for std::array with non size_t integer
I'm trying to adapt the solution presented in Avoiding struct in variadic template function to my need. However, I can't understand the the behavior of G++. Consider the following function:
template
int nextline(const…
hivert
- 10,579
- 3
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6
votes
3 answers
c++ templated constructor error
More templated woes... I love C++, but sometimes I hate it.
I cannot figure out why the compiler is complaining here, and what I can do about it.
struct blah
{
template
blah(void(*)(t), t){}
};
void Func(int i) {}
void Func2(int&…
Tyson Jacobs
- 352
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5
votes
3 answers
Template argument deduction
I'm currently facing a problem I haven't been able to solve myself.
Basically what I'm trying to do is implement some linq-like behaviour in C++.
I'll start off with the code in my header:
template class A,
…
Tom Knapen
- 2,277
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5
votes
2 answers
Is it possible to deduce whether type is incomplete without compilation failure?
I want to achieve behavior like sizeof(complete_type) will return real sizeof, and sizeof(incomplete_type) - will be just 0
I need this to provide extended run time type information for IPC(inter-process) communication with the description structure…
dev_null
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5
votes
1 answer
C++ Type vs. Non-Type Template Deduction Question
I have a question about C++ template deduction when there are two matches: one typed and the other non-typed. In the following situation:
// First
template
void g(int a)
{
...
}
// Second
template
void g(A a)
{
...
}
int a =…
O.T.Vinta
- 217
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5
votes
0 answers
How to get the type of the first parameter of a dependent function pointer template parameter in C++11?
Current code:
#include
template
std::pair f(T * const t)
{
// ...
return std::make_pair(t, D); // need `T` and `D` here
}
void d(int *t);
void g()
{
auto something = f
eepp
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