R4RS 6.5.5  (exact->inexact number)  ==>  number
            (inexact->exact number)  ==>  number

EXACT->INEXACT returns an inexact representation of NUMBER. The
value returned is the inexact number that is numerically closest
to the argument. S9fES implements this by setting the "inexact"
flag of the number if it is a real number. If it is an integer,
it converts it to type "real" first.

INEXACT->EXACT returns an exact representation of NUMBER. The
value returned is the exact number that is numerically closest
to the argument. S9fES implements this by clearing the "inexact"
flag of the number if it is a real number. If the fraction of
the number is zero, it also converts it to an integer.
