Is there another function in Fortran like `merge` that does not evaluate its arguments?

[certik]

@Beliavsky, @everythingfunctional see this thread for more “fun” examples of side-effect-free, but not deterministic functions and what it leads to:

Pure functions not deterministic in serial and parallel loops

Here is a simple example that applies a pure (even elemental) function to each element of an array three different ways (elemental, do concurrent, openmp loop) and you get three different results: program test_pure implicit none integer, parameter :: n = 16 integer :: i, A(n) A = 1 A = h(A) print *, A A = 1 do concurrent (i = 1:n) A(i) = h(A(i)) end do print *, A A = 1 !$OMP PARALLEL DO do i = 1,n A(i) = h(A(i)) end do !$OMP END PARALLEL DO print *, A contains elemental intege…