A component represents a source file or
(recursively) a collection of components.
A system is (roughly speaking) a top-level component
that can be found via
A system designator is a system itself, or a string or symbol that behaves just like any other component name (including with regard to the case conversion rules for component names).
A component designator, relative to a base component, is either a component itself, or a string or symbol, or a list of designators.
Given a system designator,
find-systemfinds and returns a system. If no system is found, an error of type
missing-componentis thrown, or
nilis returned if
To find and update systems,
find-systemfuncalls each element in the
*system-definition-search-functions*list, expecting a pathname to be returned, or a system object, from which a pathname may be extracted, and that will be registered. The resulting pathname (if any) is loaded if one of the following conditions is true:
- there is no system of that name in memory
- the pathname is different from that which was previously loaded
- the file's
last-modifiedtime exceeds the
last-modifiedtime of the system in memory
When system definitions are loaded from .asd files, a new scratch package is created for them to load into, so that different systems do not overwrite each others operations. The user may also wish to (and is recommended to) include
in-packageforms in his system definition files, however, so that they can be loaded manually if need be.
The default value of
*system-definition-search-functions*is a list of two functions. The first function looks in each of the directories given by evaluating members of
*central-registry*for a file whose name is the name of the system and whose type is asd. The first such file is returned, whether or not it turns out to actually define the appropriate system. The second function does something similar, for the directories specified in the
source-registry. Hence, it is strongly advised to define a system foo in the corresponding file foo.asd.
Given a base component (or designator for such), and a path, find the component designated by the path starting from the base.
If path is a component object, it designates itself, independently from the base.
If path is a string, or symbol denoting a string via
coerce-name, then base is resolved to a component object, which must be a system or module, and the designated component is the child named by the path.
If path is a
find-componentwith the base and the
carof the path, and the resulting object is used as the base for a tail call to
carof the path.
If base is a component object, it designates itself.
If base is null, then path is used as the base, with
nilas the path.
If base is a string, or symbol denoting a string via
coerce-name, it designates a system as per
If base is a
conscell, it designates the component found by
caras base and