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Description
Related to a Fortran Discourse thread, I think a same_shape function that takes two array arguments and returns .TRUE. if the arguments have the same shape or if the 2nd argument is not PRESENT would be useful. It would make it easier to check array dimensions upon entering a procedure, including array dimensions of optional arguments. Making it easier could make it more likely that programmers do it. Below is an example for real arrays up to dimension 3, but it should be available for dimension up to say 7 and for all pairs of basic types, since one may want to check that a real and integer array have the same shape.
A rationale for same_shape is that if array y is not PRESENT, the expression
all(shape(x) == shape(y))
is invalid. Instead you could write
same_shape(x,y)
interface same_shape
module procedure same_shape_real_real_1d, same_shape_real_real_2d, &
same_shape_real_real_3d
end interface same_shape
pure function same_shape_real_real_1d(x,y) result(tf)
! true if x(:) and y(:) have the same shape or y not PRESENT
real(kind=dp), intent(in) :: x(:)
real(kind=dp), intent(in), optional :: y(:)
logical :: tf
if (present(y)) then
tf = size(x) == size(y)
else
tf = .true.
end if
end function same_shape_real_real_1d
!
pure function same_shape_real_real_2d(x,y) result(tf)
! true if x(:,:) and y(:,:) have the same shape or y not PRESENT
real(kind=dp), intent(in) :: x(:,:)
real(kind=dp), intent(in), optional :: y(:,:)
logical :: tf
if (present(y)) then
tf = all(shape(x) == shape(y))
else
tf = .true.
end if
end function same_shape_real_real_2d
!
pure function same_shape_real_real_3d(x,y) result(tf)
! true if x(:,:,:) and y(:,:,:) have the same shape or y not PRESENT
real(kind=dp), intent(in) :: x(:,:,:)
real(kind=dp), intent(in), optional :: y(:,:,:)
logical :: tf
if (present(y)) then
tf = all(shape(x) == shape(y))
else
tf = .true.
end if
end function same_shape_real_real_3d