Tells the dspec system of the source location.
at-location (location) &body body => result
A pathname or a keyword.
Forms, including defining forms.
The result of body.
at-location informs the dspec system that the source for definitions done during the execution of body are at the location location.
location is usually a pathname, for definitions occurring in a file or editor buffer with that pathname.
Other locations are reserved for internal use. These are:
An editor buffer
Defined in an editor buffer with no pathname.
Defined without dspec information being recorded.
An aggregate defined by the existence of a part.
:inside dspec loc)
A subform of dspec at location loc.
LispWorks User Guide and Reference Manual - 13 Feb 2015