[Chicken-users] From inexact to exact using the "-" procedure?

[Jeronimo Pellegrini]

Hello,

I'm not sure if this is a bug or a feature:

#;1> (use numbers)
#;2> (define y (* 0.1 1+1i))
#;3> (define a (+ 1 y))
#;4> (define b (+ 2 y))
#;5> (- a b)
1.0
#;6> (exact? (- a b))
#f

That's what I expected... The imaginary part vanished,
but it's like doing (- 0.1 0.1) -- it's not exact!

Now...

#;7> (- 1+0.1i 2+0.1i)
-1
#;8> (exact?  (- 1+0.1i 2+0.1i))
#t

Well, that's supposed to be exactly the same thing,
so why is it exact? Is this an optimization?

Thanks,
J.