pointer and built-in functions

[Pablo Bonilla]

Dear all,
I am trying to create a pointer that points to different functions (e.g., max, min, sum, mean). However, when it is pointing to function sum(), I got an error.

mata:
   func = &max()  // works fine
   func = &min()  // works fine
   func = &mean() // works fine
   func = &sum()  // <-- ERROR
end

The error says

sum() built-in, may not evaluate address
(0 lines skipped)

I found a way around it by creating a wrapper function like the one below, but I still would like to know why built-in functions do not allow to be ‘pointed’ and if there is a more elegant way to solve this issue.

      function _msum(numeric matrix Z) {
        real matrix T
        T = sum(Z)
        return(T)
     }

Thanks,

[Joseph Coveney]

If you type

help m2_ftof

and scroll down to the header Passing built-in functions, you'll get your answer to your second question.

My guess regarding the first is that those Mata functions that are written in compiled C/C++ cannot be pointed to from the outside, i.e., Mata.

[Pablo Bonilla]

That's awesome, Joseph. Thank you so much for your quick and clear response. The solution is way more elegant than mine...

Thanks!