Numeric Range

A header-only C++ library that enables the representation of a range of values in a linear space (via the NumericRange class).

The linear space, of type T, must have a well-defined operator< to enable sorting and comparison of ranges (via the NumericRangeComparator). Hence while this library could be used for a variety of types, numeric types are the only ones with correctness guarantees for the classes and methods shipped in this version of the library.

Structure

A numeric range is represented by a lower bound and upper bound of value type T, as well as booleans defining whether these bounds are inclusive or exclusive, respectively.

template<typename T>
class NumericRange
{
public:
    T lb;
    bool lb_inclusive;
    T ub;
    bool ub_inclusive;
};

NumericRange<int> zero_to_one{0, true, 1, false};

Scalars

A special exception is made for a "scalar", which represents a single value in the linear space of type T. For a scalar, the lower bound equals the upper bound and both bounds are inclusive.

NumericRange<int> scalar_one{1, true, 1, true};

Ordering

Numeric ranges can also be ordered as long as they do not overlap. This is implemented by the comparator class NumericRangeComparator. If the ranges do overlap, comparing them throws an std::runtime_error.

NumericRangeComparator comp;
NumericRange<int> zero_to_one{0, true, 1, false};
NumericRange<int> one_to_two{1, true, 2, false};

assert(comp(zero_to_one, one_to_two));

A special exception is made for scalars so that NumericRangeComparator can be used to determine whether a scalar is included in a range.

NumericRangeComparator comp;
NumericRange<int> zero_to_two{0, true, 2, false};
NumericRange<int> scalar_one{1, true, 1, true};

assert(!comp(scalar_one, zero_to_two)); // comp returns false
assert(!comp(zero_to_two, scalar_one)); // comp returns false again

The result of this is that scalar 1 is neither less than nor greater than [0, 2). This can be useful when dealing with a container of ranges that are being indexed with scalars. This is demonstrated in the example program range_map.cpp.

Limitations

A numeric range or a comparison of ranges must not violate these constraints:

1. In a range, the lower bound must be <= the upper bound.
2. If a range's lower bound == upper bound, both bounds must be inclusive.
3. Overlapping ranges cannot be compared.
4. This library has only been tested with the default numeric types in C++. Using other custom types may result in unexpected or undefined behavior.

License and Contributing

This library is provided under the MIT License. Contributions are welcome, please open a relevant issue or PR.