How Can Template Functions Be Used as Template Arguments in C ?

Template Functions as Template Arguments

Problem:

In C , how can a template function be utilized as a template argument to achieve code reuse while maintaining generic functionality, particularly when the involved functions themselves are also templates?

Solution:

To address this problem, employ a template template parameter. The primary concept is that template parameters cannot directly include template template functions due to the need for prior instantiation. A workaround involves using dummy structures to encapsulate the template function:

Code Example:

<code class="cpp">template <typename T>
struct a {
    static void foo(T = T()) {}
};

template <typename T>
struct b {
    static void foo(T = T()) {}
};

struct SomeObj {};
struct SomeOtherObj {};

template <template <typename P> class T>
void function() {
    T<SomeObj>::foo();
    T<SomeOtherObj>::foo();
}

int main() {
    function<a>();
    function<b>();
}</code>

In this example, the structures a and b implement template functions for the foo method. The function template takes a template template parameter, allowing us to pass the a and b templates as arguments. Within function, specific instances of the dummy structures are created, enabling the invocation of foo with different parameter types.

Advantages:

1. Code Reusability: This approach avoids code duplication by consolidating similar functionality into a single template.
2. Genericity: The use of templates allows the function to operate on various data types and template instances, enhancing flexibility.
3. Compiler Optimization: Templates can enable compiler optimizations like inline function expansion, resulting in improved performance.

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