fypp macros for dealing with Fortran optional arguments

test_optval.fypp

#! Can be used currently
#:def optval(lhs,opt,default)
  ${lhs}$ = ${default}$
  if (present(${opt}$)) ${lhs}$ = ${opt}$
#:enddef

#! This is the F202X conditional expression syntax
#:def optval2(opt,default)
 present(${opt}$)) ? ${opt}$ : ${default}$
#:enddef

subroutine demo(left)
  integer, intent(in), optional :: left
  integer :: l 

  @:optval(l, left, 1)

  l = @{optval2(left, 1)}@ ! result

end subroutine