Decomposing Attributed Variables

## 16.5 Decomposing Attributed Variables

The attributes of an attributed variable can be accessed using one-way unification in a matching clause, e.g.

>         get_attribute(X{Name:Attribute}, A) :-
>             -?->
>             A = Attribute.

This clause succeeds only when the first argument is an attributed variable, and it binds `X` to the whole attributed variable and `A` to the attribute with name `Name`. Note that a normal (unification) clause can not be used to decompose an attributed variable (it would create a new attributed variable and unify this with the caller argument, but the unification is handled by an attributed variable handler, see Section 16.7).