Is There a More Efficient Way to Test for Integer Range Inclusion?

Testing for Range Inclusion with Enhanced Efficiency

To determine if an integer falls within a specified range, a common practice in programming languages like C and C involves comparing it against the start and end points of the range. While this approach is straightforward, it's not the most efficient.

Introducing a More Efficient Technique

An alternative method for testing range inclusion involves using a single comparison, significantly reducing the computational overhead. This technique relies on bitwise operations and effectively converts the number and the range to a point of origin. If the converted number is negative or larger than the difference between the range's upper and lower bounds, it indicates that the number lies outside the specified range.

Code Implementation

Below is an implementation of this technique in C/C :

if ((unsigned)(number - lower) <= (upper - lower))
    in_range(number);

Optimization Considerations

In practice, the efficiency gains are marginal, particularly in modern systems that use twos complement representation for integers. However, in specific scenarios where speed is crucial, this technique can provide a noticeable improvement. Pre-calculating the difference between the range's upper and lower bounds outside of any loops can further enhance performance.

Conclusion

This optimized method for testing range inclusion leverages bitwise operations to minimize computational overhead. While the speed gain may be small in most cases, it can be beneficial in performance-sensitive applications.

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