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Aleksandar Donev <[log in to unmask]> wrote: ... >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. This clouds readability to some extent. >What do you recommend? Both the latter cloud legibility to some extent. If the language had rational arithmetic, the first form would be the clearest (since it probably corresponds directly to the documentation or the mathematical formula). The second form directly expresses the desired operation, but is rather verbose. The third form is less cluttered, but doesn't explicitly specify the internal machinations of the conversions. I would suggest another form as a possibility (not strongly to be favored, but merely another alternative): y = (k-1) * x / (k+1) I would recommend whichever the maintainer of the code finds most legible. (I prefer my last suggestion, but that's because it's what I use most often. I have no evidence that any are inherently superior. Though I suspect the verbose form might be inferior.) -- J. Giles %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%