UnifyingNumbers

Unifying Numbers

The concept of unifying numbers is converting them to a common number type without losing information.

The following graph shows the hierarchy of number types in Kotlin DataFrame. The order is top-down from the most complex type to the simplest one.

          (BigDecimal)
           /      \
    (BigInteger)   \
       /   \        \
<~ ULong   Long ~> Double ..
..   |    /   |   /   |  \..
  \  |   /    |  /    |
    UInt     Int    Float
..   |    /   |   /      \..
  \  |   /    |  /
   UShort   Short
     |    /   |
     |   /    |
   UByte     Byte
       \     /
       \    /
      Nothing

For each number type in the graph, it holds that a number of that type can be expressed losslessly by a number of a more complex type (any of its parents). This is either because the more complex type has a larger range or higher precision (in terms of bits).

There are variants of this graph that exclude some types, such as BigDecimal and BigInteger. In these cases Double could be considered the most complex type. Long/ULong and Double could be joined to Double, potentially losing a little precision, but a warning will be given.

See UnifiedNumberTypeOptions for these settings.

Nullability, while not displayed in the graph, is also taken into account. This means that Int? and Float will be unified to Double?.

At the bottom of the graph is Nothing. This can be interpreted as "no type" and can have no instance, while Nothing? can only be null.