Questions tagged [default-template-argument]
16 questions
3
votes
1 answer
Non-defaulted template params after a defaulted param: class vs function
From this page on cppreference about default template arguments:
If the default is specified for a template parameter of a primary class
template, [...] each subsequent template parameter must have a default
argument, except the very last one may…
paolo
- 2,345
- 1
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- 17
3
votes
3 answers
Defaulted Template in Template Function Requires Empty Angle Brackets <>
gcc 11.2 can't seem to compile this:
template
struct Test {};
template void foo(T& bar) {}
int main()
{
Test t;
foo(t);
}
but has no problem with
template
struct Test {};
template…
Radrich
- 61
- 4
3
votes
1 answer
How to provide a default parameter argument when the type of that parameter is a template type?
template
class Pair {
public:
Pair(const K& key, const V& value = initial) { // what should "initial" be here?
// ...
}
}
For example if I use the class like this:
int main() {
Pair…
roniabusayeed
- 83
- 5
3
votes
3 answers
Special overload for pointer types
Consider the following snippet:
template
struct remove_pointer
{
};
template
struct remove_pointer
{
typedef T type;
};
template
T
clone(const T& v)
{
return v;
}
template
user3612643
- 5,096
- 7
- 34
- 55
2
votes
1 answer
CTAD fails for templated base class
Consider the following simple construct. I derive a class type EntityView from Entity which allows me to specify an allocator if I want to, and if I don't it should fall back to the defaulted template parameter. Yet the compiler complains that it…
glades
- 3,778
- 1
- 12
- 34
2
votes
1 answer
template specialization and default template parameters and sfinae
I have put together an example on creating a base template with a number of specializations.
#include
template
struct foo {
static void apply() {
std::cout << "a: " << __FUNCTION__ <<…
Blair Davidson
- 901
- 12
- 35
1
vote
1 answer
default template argument and parameter pack
In a classic recursive template specialization I need one type multiple times in the class definition, e.g. for inheriting and using statement, maybe on other places also.
Example:
template < typename ... T >
class C;
template < typename FIRST,…
Klaus
- 24,205
- 7
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- 113
1
vote
1 answer
Declaring a default templated function
Suppose I have the following:
// Foo.h
struct Foo {};
// Bar.h
struct Bar {
template ::value>::type>
void foobar();
};
// Bar.hpp
// ...?
void Bar::foobar() {}
How do…
Yves Calaci
- 1,019
- 1
- 11
- 37
0
votes
3 answers
multiple default template argument cases that depend on a template argument respectively
I would like to define two particular default cases for a template class A.
Is something similar possible?:
template
class A{
// ...
};
struct X;
// if necessary, I can also define X right here.
template<>
A =…
kaisong
- 65
- 6
0
votes
2 answers
How to make C++ template type to default to previous template type
Is there any way, to default second template type to the type of the first template argument type, to remove the need of specifying the template types when not needed?
So, I have a method, that pops values from byte array:
template
Alexander Labuuu
- 3
- 1
0
votes
1 answer
Syntax for define a template that takes a template
I wanted to create a type that holds a generic type type, that, itself, is a template with one argument. So, if my type is called C, it could be summarized like C>.
So, I went for it:
#include
template class…
Alex Vergara
- 1,766
- 1
- 10
- 29
0
votes
1 answer
CTAD doesn't work with defaulted template arguments?
Compare the following case when I have a class object that takes a vector. The non-deduced parameter T can be substituted fine with the default template argument:
#include
template
struct container
{
…
glades
- 3,778
- 1
- 12
- 34
0
votes
1 answer
C++17 pointer to tempalte class with class template default argument
I am experimenting with C++17 class template default argument and was wondering if anyone could explain:
If I have the following:
template
class MyClass { //class goes here };
And then try to use it as:
MyClass *…
Marcus Raty
- 21
- 1
0
votes
1 answer
Partial template specialization: template argument X is invalid
I want to partially specialize a class for when the first template parameter is not a POD-type. Here's what I came up with:
godbolt
#include
#include
template >
struct A
{
void…
glades
- 3,778
- 1
- 12
- 34
0
votes
1 answer
Template default argument
How do I specify a template class as a default value for a template typename? e.g. the following doesn't work.
template class X {};
template class X> class Y {};
int main()
{
…
user3689963
- 115
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- 6