Widening and Narrowing Conversions

A widening conversion changes a value to a data type that can hold all possible values of the source data. Widening conversions keep the source value but can change how it is stored. This occurs if you convert from an integer type to a floating-point type, or from Char to String.

A narrowing conversion changes a value to a data type that possibly cannot hold some values of the source data. For example, a value with a fraction is rounded when converted to an integer type.

Widening conversions

The table that follows shows the standard widening conversions.

• You can always convert a data type to that same data type.
• Conversions from integer types to floating-point types can possibly decrease precision. But such conversions do not decrease the magnitude. Thus, there is almost no risk of missing data.

Widening conversions do not cause errors at run-time.

Narrowing conversions

Narrowing conversions can cause errors at run-time. They can cause exceptions or missing data. An error occurs if the end data type cannot receive the converted value. For example, a number conversion can cause overflow. The compiler does not let you do narrowing conversions automatically.

When to use narrowing conversions

TODO

Exceptions during conversion

TODO

• BadCastError
• OverflowError

Reference type conversions

TODO

See also

• Automatic and Special Conversions