The type macro is a special Verse construct that can be used to define functions or construct new types from existing types using where clauses. The type macro can be used anywhere a type can be used. For example, the following example constructs a new type using a where clause, then uses that type in a function:

|  |  |
| --- | --- |
|  | # Construct a new type with a where clause |
|  | uint8 := type{X:int where 0 <= X, X < 256} |
|  |  |
|  | # Define a new function using uint8 |
|  | Foo():uint8 = 0 |

Construct a new type with a where clause

uint8 := type{X:int where 0 <= X, X < 256}

Define a new function using uint8

Foo():uint8 = 0

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There where clause is only supported in function parameter definitions or as a range condition on numeric types.

The following example uses the type macro to define a function as an argument to a new function:

|  |  |
| --- | --- |
|  | # Define a function with type |
|  | Bar(X:type{_():uint8}):uint8 = X() |
|  |  |
|  | # Call Bar with Foo argument |
|  | Y := Bar(Foo) |

Define a function with type

Bar(X:type{_():uint8}):uint8 = X()

Call Bar with Foo argument

Y := Bar(Foo)