close2 close2 - 1 month ago 17
C++ Question

functions as template arguments

I have a TaskWrapper:

template <typename T, T (*F)(T)>
struct TaskWrapper {
static inline T run(T clock) {
return F(clock);
}
};


to use it I have to specify the T template argument:

uint16_t task1(uint16_t clock) { return clock + 1; }
typedef tasks::TaskWrapper<uint16_t, task1> Task;


I would like to simply write:

typedef tasks::TaskWrapper<task1> Task;


and let the compiler figure out that the return and argument type is uint16_t.

Notes:

The TaskWrapper is obviously simplified and in reality has a few other arguments, which are passed during the typedef.

The wrapped functions can only be:

uint8_t task(uint8_t clock);
uint16_t task(uint16_t clock); // or
uint32_t task(uint32_t clock);


The TaskWrapper is passed as template argument to another class, which will at some point call Task::run(...);

C++11 would be fine.

Answer

Only since C++17's template <auto> feature:

template <auto F>
struct TaskWrapper {
  template <typename T>
  static inline auto run(T clock) {
    return F(clock);
  }
};

uint16_t task1(uint16_t clock) { return clock + 1; }
typedef TaskWrapper<&task1> Task; // ok
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