
rational(+Number, -Result)

   Converts Number into a rational number and unifies it with Result.



Arguments
   Number              A number.
   Result              Output: rational number.

Type
   Arithmetic

Description
   This predicate is used by the ECLiPSe compiler to expand evaluable
   arithmetic expressions.  So the call to rational(Number, Result) is
   equivalent to

    Result is rational(Number)

    which should be preferred.

   When Number is an integer, Result is a rational with denominator 1.

   When Number is already a rational, Result is identical to Number.

   When Number is a float, Result is a rational whose value is exactly equal
   to the value of the floating-point number. Since floats are usually
   approximations of the intended value, the results may look unintuitive
   and have unnecessarily large numerators and denominators. Use rationalize/2
   to produce the most compact rational that still converts back into the
   original float. rational/2 is usually faster than rationalize/2.

   Bounded reals cannot be converted to rationals.

   In coroutining mode, if Number is uninstantiated, the call to
   rational/2 is delayed until this variable is instantiated.


Modes and Determinism
   rational(+, -) is det

Exceptions
     4 --- Number is not instantiated (non-coroutining mode only).
    24 --- Number is not of a numeric type.
   141 --- Number is a bounded real

Examples
   
Success:
    Result is rational(25).	% gives Result = 25_1
    Result is rational(1.5).	% gives Result = 3_2
    Result is rational(3_4).	% gives Result = 3_4
    Result is rational(9_12).	% gives Result = 3_4
    Result is rational(-6).	% gives Result = -6_1
    Result is rational(0.1).    % gives Result = 3602879701896397_36028797018963968

Error:
    Result is rational(0.9__1.1, X).     % unimplemented


See Also
   rationalize / 2, is / 2
