
/(+Number1, +Number2, -Result)

   Evaluates the quotient Number1 / Number2 and unifies the resulting value
with Result.



Arguments
   Number1             A number.
   Number2             A number.
   Result              Output: float (or rational).

Type
   Arithmetic

Description
   This predicate is used by the ECLiPSe compiler to expand evaluable
   arithmetic expressions.  So the call to /(Number1, Number2, Result) is
   equivalent to

    Result is Number1 / Number2

    which should be preferred for portability.

   If both arguments are integers, then the result is of type float
   by default (coinciding with ISO-Prolog).  This can be changed by
   switching the global flag 'prefer_rationals' to 'on': the result
   is then of rational type, and therefore precise.  In practice,
   a better way to enforce a rational result is by explicitly
   converting one or both arguments to a rational before dividing,
   e.g. Z is rational(X)/Y.

   The following table details the behaviour on zero-division,
   depending on the argument types.  The exact result depends on
   the result's type ability to represent extreme values.

      -3 / 0                        -1.0Inf (negative infinity)
       0 / 0                        arithmetic exception
       3 / 0                         1.0Inf (positive infinity)

      -3.0 / 0.0                    -1.0Inf (negative infinity)
      -0.0 / 0.0                    arithmetic exception
       0.0 / 0.0                    arithmetic exception
       3.0 / 0.0                     1.0Inf (positive infinity)
      -3.0 / -0.0                    1.0Inf (positive infinity)
      -0.0 / -0.0                    arithmetic exception
       0.0 / -0.0                    arithmetic exception
       3.0 / -0.0                   -1.0Inf (negative infinity)

      rational(-3) / rational(0)    representation error
      rational( 0) / rational(0)    arithmetic exception
      rational( 3) / rational(0)    representation error

      breal(-3) / breal(0)          -1.0Inf__-1.0Inf (negative infinity)
      breal( 0) / breal(0)          -1.0Inf__1.0Inf (undefined)
      breal( 3) / breal(0)           1.0Inf__1.0Inf (positive infinity)

   Dividing infinity by infinity yields the same result as 0/0.

   In coroutining mode, if Number1 or Number2 are uninstantiated,
   the call to //3 is delayed until these variables are instantiated.



Modes and Determinism
   /(+, +, -) is det

Exceptions
     4 --- Number1 or Number2 is not instantiated (non-coroutining mode    only).
    24 --- Number1 or Number2 is not of a numeric type.
    20 --- Illegal arithmetic operation:  0/0 or infinity/infinity

Examples
   
Success:
    Result is 10 / 2.		% gives Result = 5.0
    Result is 10 / -2.0.	% gives Result = -5.0
    Result is 9 / 12.		% gives Result = 0.75

    % with set_flag(prefer_rationals, on):
    Result is 9 / 12.		% gives Result = 3_4

Error:
    Result is 2/0.              % arithmetic exception


See Also
   is / 2, get_flag / 2, set_flag / 2
