bekoeppel / numeral

numeral -- Generic Numbers library

numeral is a simple Java library to offer arithmetic operations that can be used with generic numbers.

I wanted to do something like this:

// does not compile
public <N extends Number> List<N> getBuckets(N start, N end, N step) {
    
    List<N> buckets = new ArrayList<N>();
    // Error: Operator '<=' can not be applied to 'N', 'N'
    while(start <= end) {
        buckets.add(start);
        // Error: Operator '+' can not be applied to 'N', 'N'
        start += step;
    }
    
    return buckets;
}

I needed this method to be able to generate List as well as List. However, the arithmetic operation + in i + j happen on the unboxed types of i and j, and the Number class doesn't have instance methods to perform those operations.

With Numeral, I can write the following:

public <N extends Numeral> List<N> getBuckets(N start, N end, N step) {
    
    List<N> buckets = new ArrayList<N>();
    while(start.smallerOrEqualThan(end)) {
        buckets.add(start);
        start = start.add(step);
    }
    
    return buckets;
}

And then use this with

NumeralDouble start = new NumeralDouble(2.72);
NumeralDouble end = new NumeralDouble(3.14);
NumeralDouble step = new NumeralDouble(0.1);

List<NumeralDouble> buckets = getBuckets(start, end, step);

numeral suffers from the following problems. Hence, the library is not meant for performance intensive applications.

• Performance
• Garbage collector overhead
• no autoboxing / unboxing