The type must be a model of .

A PrimitiveTransform is a class type that has a nested class template called `impl<>` that takes three template parameters representing an expression type, a state type and a data type. Specializations of the nested impl template are ternary monomorphic function objects that accept expression, state, and data parameters. A PrimitiveTransform is also a PolymorphicFunctionObject implemented in terms of the nested `impl<>` template.

The return type of the overloaded function call operator.

Applies the transform.
Applies the transform.
Applies the transform.
Applies the transform.