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How to check if variable is of string type in template class?


By : fillhora
Date : September 16 2020, 10:00 PM
like below fixes the issue You don't need to know the type, you just need to use a better initializer. Instead of using 0, use T{} or {} instead like
code :
vec(const size_t size_ = 0): _size(size_), values(_size? new T[_size]:0){
    for(size_t i = 0; i < _size; i++)
        values[i] = T{}; // or values[i] = {};
}
vec(const size_t size_ = 0): _size(size_), values(_size? new T[_size]{} : 0) {}


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How to check type directly from type that passed through template function not from variable?


By : senju hashirama
Date : March 29 2020, 07:55 AM
like below fixes the issue I think you want something like this (using type traits):
The following section of code must be put outside of the class section.
code :
template <typename T>
struct EnemyTraits { };

template <>
struct EnemyTraits<Zombie01> { static const int pop_type = ZOMBIE; };

template <>
struct EnemyTraits<Vampire01> { static const int pop_type = VAMPIRE; };
template <typename T> T* ObjectSpawner::spawnEnemy(SpawnDirection dir)
{
    if(_enemiesPool->isAnyFreeObjects())
    {
        const int pop_type = EnemyTraits<T>::pop_type;
        return dynamic_cast<T*>(_enemiesPool->popFreeObjectAndAddToActiveListForType(pop_type));
    }
    else
        return NULL;
}

How to get the type of a template, like template <typename T>, and to check if T is int or float or a class


By : Lara
Date : March 29 2020, 07:55 AM
With these it helps To print the int and float values just provide overloads of display() that take arguments of those types, respectively. For objects that contain a member function named display(), you can use SFINAE to selectively enable the free function form of display()
code :
#include <iostream>
#include <type_traits>

template<typename T>
auto display(T const& t) -> decltype(t.display(), void())
{
    std::cout << "display(T const& t)\n";
}

void display(int)
{
    std::cout << "display(int)\n";
}

void display(double)
{
    std::cout << "display(double)\n";
}

struct foo
{
    void display() const
    {
        std::cout << "foo::display\n";
    }
};

struct bar {};

int main()
{
    display(10);
    display(10.0);
    display(foo());
//    display(bar()); // doesn't compile
}
main.cpp:35:18: error: no matching function for call to 'display(bar)'

     display(bar()); // doesn't compile
...
main.cpp:5:49: error: 'const struct bar' has no member named 'display'

calling a template function on a auto type-inferred variable in a template class


By : DemonZer0
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further The compiler doesn't know that ref.foo is a template, so you need to tell it:
code :
ref.foo<1>();
//change to
ref.template foo<1>();

Is it possible to check if a object is equal to a template class without specifying the template type?


By : Thooms
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further Suppose I have the class: , Something along these lines:
code :
template <typename T>
struct IsChartData : public std::false_type {};

template <typename T>
struct IsChartData<ChartData<T>> : public std::true_type {};

if (IsChartData<decltype(value)>()) {...}

How can I check if a template type parameter is a character type or a string type?


By : Lakshmikanth Reddy P
Date : March 29 2020, 07:55 AM
To fix this issue I am trying to write code that will be able to distinguish between character types (char, wchar_t, etc.), string types (std::string, std::wstring, etc.), and numeric types, so I can enclose characters in single-quotes and strings in double-quotes. The idea is to treat values differently depending on how they are output. Characters and strings are fundamentally different from numeric values, because they display according to an encoding representation of their contents (i.e., ASCII, Unicode, UTF, etc.), rather than as numeric values.
code :
template<class T>struct tag_t{};
template<class T>constexpr tag_t<T> tag{};
namespace detect_string {
  template<class T, class...Ts>
  constexpr bool is_stringlike(tag_t<T>, Ts&&...){ return false; }
  template<class T, class A>
  constexpr bool is_stringlike( tag_t<std::basic_string<T,A>> ){ return true; }
  template<class T>
  constexpr bool detect=is_stringlike(tag<T>); // enable ADL extension
}
namespace detect_character {
  template<class T, class...Ts>
  constexpr bool is_charlike(tag_t<T>, Ts&&...){ return false; }
  constexpr bool is_charlike( tag_t<char> ){ return true; }
  constexpr bool is_charlike( tag_t<wchar_t> ){ return true; }
  // ETC
  template<class T>
  constexpr bool detect=is_charlike(tag<T>); // enable ADL extension
}
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