provide, requireFunction


    provide module-name implementation-dependent

    require module-name &optional pathname-list implementation-dependent

    Arguments and Values

    module-name — a string designator.

    pathname-listnil, or a designator for a non-empty list of pathname designators. The default is nil.


    provide adds the module-name to the list held by *modules*, if such a name is not already present.

    require tests for the presence of the module-name in the list held by *modules*. If it is present, require immediately returns. Otherwise, an attempt is made to load an appropriate set of files as follows: The pathname-list argument, if non-nil, specifies a list of pathnames to be loaded in order, from left to right. If the pathname-list is nil, an implementation-dependent mechanism will be invoked in an attempt to load the module named module-name; if no such module can be loaded, an error of type error is signaled.

    Both functions use string= to test for the presence of a module-name.

    ;;; This illustrates a nonportable use of REQUIRE, because it 
    ;;; depends on the implementation-dependent file-loading mechanism. 
    (require "CALCULUS") 
    ;;; This use of REQUIRE is nonportable because of the literal 
    ;;; physical pathname. 
    (require "CALCULUS" "/usr/lib/lisp/calculus") 
    ;;; One form of portable usage involves supplying a logical pathname, 
    ;;; with appropriate translations defined elsewhere. 
    (require "CALCULUS" "lib:calculus") 
    ;;; Another form of portable usage involves using a variable or 
    ;;; table lookup function to determine the pathname, which again 
    ;;; must be initialized elsewhere. 
    (require "CALCULUS" *calculus-module-pathname*)
    Side Effects

    provide modifies *modules*.

    Affected By

    The specific action taken by require is affected by calls to provide (or, in general, any changes to the value of *modules*).

    Exceptional Situations

    Should signal an error of type type-error if module-name is not a string designator.

    If require fails to perform the requested operation due to a problem while interacting with the file system, an error of type file-error is signaled.

    An error of type file-error might be signaled if any pathname in pathname-list is a designator for a wild pathname.

    See Also

    *modules*, Section 19.1.2 (Pathnames as Filenames)


    The functions provide and require are deprecated.

    If a module consists of a single package, it is customary for the package and module names to be the same.