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unit

🌌unit

unit -- value to be used as result of features that do not return a result

NOTE: unit corresponds to type void in C, Java, etc.

unit is the preferred result type for features that return without producing
a result value. These are features that typically have an outside effect
such as

println(String s) unit is ...

or features that change the state of an instance such as

increment(delta i64) unit is
set counter := counter + delta

The Fuzion language implementation automatically inserts code that returns the
unit value as a result of these features, there is no need for an explicit unit
result as in

increment(delta i64) unit is
set counter := counter + delta
unit

but it is allowed to return unit explicitly if desired.

Another application of the unit type are generic features when certain generic
values are not needed and can be ignored. An example could be a generic map
implementation map<K,V> that maps values of type K to values of type V. Using
unit as the actual generic argument for V, e.g., map<string,unit> creates a
map that stores no data for each key, which essentially turns the map into a
set of the map's keys.

The Fuzion library knows several different unit types. Another example is nil,
which is used as the alternative type in an option. This enables the use of
option<void>, which can store two distinct values, void and nil.

Other unit types in Fuzion are TRUE and FALSE.

The simplest syntax to create a value of unit type is an empty block '{}'. Note
that an empty tuple 'tuple<>' is a different unit value of a different type and
the syntax '()' is (at least for now) not supported.

Please note the fundamental difference between

red is {}
red => {}

The first declares a feature red that defines a new unit type red, the second
declares a feature red with result type unit, i.e., a synonyme for unit as in

red unit is {}

The memory required to store a value of unit type is 0 bits, so you can use
plenty without worrying about space constraints. The Fuzion code generators
typically will not generate any code for returning or assiging a value of unit
type, so these are very efficient as well.

human readable string