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@x:Act does not support type inheritance. Instead, an alterative mechanism called views are provided. Here is a simple example that produces a view of the int type that restricts the values to only those that are even.


@x:view even {
   @x:func sys:Is(v~int),visible {
      v /+ 2 == 0
   }
}
2~even; eol;
5?even; eol;
10?even; eol

The special "sys:Is" function states what values are "in" the view. The /+ is the remainder operation.

The infix ~ operation asserts that its left operand has the type or view specified by the right operand and returns the value of the left operand. The infix ? operator tests if its left operand has the type or view specified by the right operand.