[ Arithmetic | The ECLiPSe Built-In Predicates | Reference Manual | Alphabetic Index ]

getbit(+Number, +Index, ?Result)

Result is the Index'th bit of Number.
+Number
Integer.
+Index
Non-negative integer.
?Result
A variable or integer.

Description

Returns the Index'th bit of Number, assuming binary two's complement representation. The least significant bit has index zero. The result is either 0 or 1. This predicate is used by the ECLiPSe compiler to expand evaluable arithmetic expressions. So the call to getbit(Number, Index, Result) is equivalent to 
    Result is getbit(Number, Index)
which should be preferred.

In coroutining mode, if Number or Index are free variables, the call 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
Number or Index is not instantiated (non-coroutining mode only).
(5) type error
Result is a number but not an integer.
(5) type error
Number or Index is a number but not an integer.
(24) number expected
Number or Index is not of a numeric type.
(24) number expected
Result is neither a number nor a variable.

Examples

Success:
      getbit(10, 3, 1).
      getbit(10, 2, 0).
      getbit(10, 99, 0).

See Also

is / 2, clrbit / 3, setbit / 3