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#### 11.2.18 use-package [Function]

`use-package` packages-to-use &optional package ⇒ t

#### Arguments and Values::

packages-to-use—a designator for a list of package designators. The `KEYWORD` package may not be supplied.

package—a package designator. The `KEYWORD` package cannot be supplied. The default is the current package.

#### Description::

use-package causes package to inherit all the external symbols of packages-to-use. The inherited symbols become accessible as internal symbols of package.

Packages-to-use are added to the use list of package if they are not there already. All external symbols in packages-to-use become accessible in package as internal symbols. use-package does not cause any new symbols to be present in package but only makes them accessible by inheritance.

use-package checks for name conflicts between the newly imported symbols and those already accessible in package. A name conflict in use-package between two external symbols inherited by package from packages-to-use may be resolved in favor of either symbol by importing one of them into package and making it a shadowing symbol.

#### Examples::

     (export (intern "LAND-FILL" (make-package 'trash)) 'trash) ⇒  T
     (find-symbol "LAND-FILL" (make-package 'temp)) ⇒  NIL, NIL
     (package-use-list 'temp) ⇒  (#<PACKAGE "TEMP">)
     (use-package 'trash 'temp) ⇒  T
     (package-use-list 'temp) ⇒  (#<PACKAGE "TEMP"> #<PACKAGE "TRASH">)
     (find-symbol "LAND-FILL" 'temp) ⇒  TRASH:LAND-FILL, :INHERITED

#### Side Effects::

The use list of package may be modified.

#### See Also::

unuse-package , package-use-list , Package Concepts

#### Notes::

It is permissible for a package P_1 to use a package P_2 even if P_2 already uses P_1. The using of packages is not transitive, so no problem results from the apparent circularity.

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