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# /(+Number1, +Number2, -Result)

Evaluates the quotient Number1 / Number2 and unifies the resulting value
with Result.
*Number1*
- A number.
*Number2*
- A number.
*Result*
- Output: float (or rational).

## 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

### Exceptions

*(4) instantiation fault *
- Number1 or Number2 is not instantiated (non-coroutining mode only).
*(24) number expected *
- Number1 or Number2 is not of a numeric type.
*(20) arithmetic exception *
- 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