I wrote:
> Notationally, 0.0 is an inexact zero and 0 is the exact zero.
> Therefore, in Scheme notation, 1.0 (i.e. 1.0+0i) has a different meaning
> than 1.0+0.0i.  In the case of 1.0, the imaginary part is known to be
> exactly zero, whereas for 1.0+0.0i the imaginary part is merely
> estimated to be approximately zero.

I should mention that Scheme implementations differ in how hard they
work to preserve exactness information.  For example, (log 1) and
(sin 0) might return either 0 or 0.0 depending on the implementation,
and (imag-part 1.0) might return either 0 or 0.0.

In many (most?) implementations, (imag-part 1.0) => 0.0, which means
that some exactness information as been lost.  In such implementations,
1.0 and 1.0+0.0i can be treated as equivalent.

     Mark

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