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> Date: Sun, 17 Sep 2000 11:54:36 -0400 > From: Aleksandar Donev <[log in to unmask]> > Hello, > > I have a pedagological question for the Fortran teachers out there. > How does one write "best" an expression with mixed types, say: > > complex(kind=sp) :: x,y > integer :: k > > y=(k-1)/(k+1)*x > > I recommend to students to explicitly write all the type conversions: > > y=cmplx(k-1,0,sp)/cmplx(k+1,0,sp)*x > > though > > y=x*(k-1)/(k+1) > > also works. Only by accident. And it's not efficient, either. One must always be careful about writing division involving integers. (k-1)/(k+1) can easily return a zero result, especially wen it's written at the start of an expression (as is your first example). Writing REAL(k+1) is sufficient in your example. Converting to complex is wasteful, and is almost unreadable. It's wasteful because two complex multiplications are introduced when simple scalar multiplication by a complex value is all that's required. > This clouds readability to some extent. > What do you recommend? > > Thanks, > Aleksandar %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%