Special

Optional

Either are empty or have a value

opt[]

Never

nev[]

The never type is a type with no values, representing the result of computations that never complete.

Union

Union is a data type that allows different data types to be stored in the same memory locations. Union provides an efficient way of reusing the memory location, as only one of its members can be accessed at a time. It uses a single memory location to hold more than one variables. However, only one of its members can be accessed at a time and all other members will contain garbage values. The memory required to store a union variable is the memory required for the largest element of the union.

We can use the unions in the following locations.

• Share a single memory location for a variable and use the same location for another variable of different data type.
• Use it if you want to use, for example, a long variable as two short type variables.
• We don’t know what type of data is to be passed to a function, and you pass union which contains all the possible data types.

var aUnion: uni[int[8], int, flt]; 

Any

any[]

Null

nil

In the current V1 compiler milestone, nil is accepted only when type checking already knows it is flowing into an opt[...] or err[...] shell. Plain inference from nil alone is not supported.

Current V1 shell note:

• opt[...] and err[...] are shell values.
• postfix unwrap value! applies to those shell values.
• routine calls declared with ResultType / ErrorType are not err[...] shells.
• use check(...) or expr || fallback for those routine calls instead of !.
• use err[...] when you need a storable error value.