How to alias and instantiate a template function at same time?

I have a template function as following:

using namespace std::chrono;
using namespace std::chrono_literals;
template <typename D>
time_point<system_clock, D> makeTime(
   int year, int month, int day, int hour = 0, int minute = 0,
   int second = 0, int ms = 0, int us = 0, int ns = 0 );

Normally, I call it like this: auto us_tp1 = makeTime<microseconds>( 2020, 5, 26, 21, 21, 21, 999, 123 );

But now I need to call it at somewhere through an alias "makeTimeUS" like this:

auto us_tp1 = makeTimeUS( 2020, 5, 26, 21, 21, 21, 999, 123 );

just like that makeTimeUS is an instance of makeTime.

I tried this:

using makeTimeUS = template time_point<system_clock, microseconds> makeTime;

and this:

using makeTimeUS = template time_point<system_clock, microseconds> makeTime(
 int, int, int, int, int, int, int, int, int );

but neither can pass the compilation.

How to instantiate a template function and give an alias on it at same time? The reason I need to do so, is that there are too many old codes calling makeTimeUS as if it be a normal function instead of a template. Thanks!

Solution

You can get a function pointer to the function you want and then use that as your "alias". That would look like:

auto makeTimeUS = makeTime<microseconds>;

And can be used like:

auto us_tp1 = makeTimeUS( 2020, 5, 26, 21, 21, 21, 999, 123 );

But this just lets you change the name. Since it is a function pointer the default arguments no longer work and you still have to specify all of the parameters.

To get around that you can make a wrapper instead of an alias using a lambda and that would look like

auto makeTimeUS = [](int year, int month, int day, int hour = 0, 
                     int minute = 0, int second = 0, int ms = 0)
                  { 
                       return makeTime<microseconds>(year, month, day, hour, minute, second, ms); 
                  };