[ Arithmetic | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]
-(+Number1, +Number2, ?Result)
Evaluates the difference Number1 - Number2 and unifies the resulting value
with Result.
- +Number1
- A number.
- +Number2
- A number.
- ?Result
- A variable or a number.
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.
The result is of type breal if any of the arguments is a breal,
else float if any of the arguments is a float, else rational if any
of the arguments is a rational. Only when both arguments are
integers is the result an integer.
In coroutining mode, if Number1 or Number2 are free variables, the call
to -/3 is delayed until these variables are instantiated.
Fail Conditions
Fails if the result of the evaluation does not unify with Result.
Resatisfiable
No
Exceptions
- (4) instantiation fault
- Number1 or Number2 is not instantiated (non-coroutining mode only).
- (5) type error
- Result is of a different type than the evaluation result.
- (24) number expected
- Number1 or Number2 is not of a numeric type.
- (24) number expected
- Result is neither a number nor a variable.
- (20) arithmetic exception
- floating point overflow
Examples
Success:
-(5, 2, 3). (gives Result = 3)
-(5, -2.0, Result). (gives Result = 7.0)
Fail:
-(1, 2, 3).
Error:
-(A, 2, 6). (Error 4).
-(1, 2, 3.0). (Error 5).
-(4 + 1, 2, 3). (Error 24).
-(5, 2, r). (Error 24).
See Also
is / 2