number—a real.
rational—a rational.
rational
and rationalize
convert
reals
to rationals.
If number is already rational, it is returned.
If number is a float,
rational
returns a rational
that is mathematically equal in value to the float.
rationalize
returns a rational that
approximates the float to the accuracy of
the underlying floating-point representation.
rational
assumes that the float is completely accurate.
rationalize
assumes that the
float is accurate only to the precision of the
floating-point representation.
(rational 0) → 0 (rationalize -11/100) → -11/100 (rational .1) → 13421773/134217728 ;implementation-dependent (rationalize .1) → 1/10
The implementation.
Should signal an error of type type-error
if number is not a real.
Might signal arithmetic-error
.
It is always the case that
(float (rational x) x) ≡ x
and
(float (rationalize x) x) ≡ x
That is, rationalizing a float by either method and then converting it back to a float of the same format produces the original number.