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cl:functions:load [2019/06/15 02:00]
cl:functions:load [2020/07/02 08:00] (current)
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 +====== Function LOAD ======
 +  * **load** //​filespec//​ ''&​key''​ //verbose// //print// //​if-does-not-exist//​ //​external-format//​ → //​generalized-boolean//​
 +====Arguments and Values====
 +  * //​filespec//​ - a //​[[CL:​Glossary:​stream]]//,​ or a //​[[CL:​Glossary:​pathname designator]]//​. The default is taken from **[[CL:​Variables:​star-default-pathname-defaults-star|*default-pathname-defaults*]]**.
 +  * //verbose// - a //​[[CL:​Glossary:​generalized boolean]]//​. The default is the //​[[CL:​Glossary:​value]]//​ of **[[CL:​Variables:​star-load-verbose-star|*load-verbose*]]**.
 +  * //print// - a //​[[CL:​Glossary:​generalized boolean]]//​. The default is the //​[[CL:​Glossary:​value]]//​ of **[[CL:​Variables:​star-load-print-star|*load-print*]]**.
 +  * //​if-does-not-exist//​ - a //​[[CL:​Glossary:​generalized boolean]]//​. The default is //​[[CL:​Glossary:​true]]//​.
 +  * //​external-format//​ - an //​[[CL:​Glossary:​external file format designator]]//​. The default is **'':​default''​**.
 +  * //​generalized-boolean//​ - a //​[[CL:​Glossary:​generalized boolean]]//​.
 +**load** //​[[CL:​Glossary:​load|loads]]//​ the //​[[CL:​Glossary:​file]]//​ named by //​filespec//​ into the Lisp environment.
 +The manner in which a //​[[CL:​Glossary:​source file]]// is distinguished from a //​[[CL:​Glossary:​compiled file]]// is //​[[CL:​Glossary:​implementation-dependent]]//​.
 +If the file specification is not complete and both a //​[[CL:​Glossary:​source file]]// and a //​[[CL:​Glossary:​compiled file]]// exist which might match, then which of those files **load** selects is //​[[CL:​Glossary:​implementation-dependent]]//​.
 +If //​filespec//​ is a //​[[CL:​Glossary:​stream]]//,​ **load** determines what kind of //​[[CL:​Glossary:​stream]]//​ it is and loads directly from the //​[[CL:​Glossary:​stream]]//​.
 +If //​filespec//​ is a //​[[CL:​Glossary:​logical pathname]]//,​ it is translated into a //​[[CL:​Glossary:​physical pathname]]//​ as if by calling **[[CL:​Functions:​translate-logical-pathname]]**.
 +**load** sequentially executes each //​[[CL:​Glossary:​form]]//​ it encounters in the //​[[CL:​Glossary:​file]]//​ named by //​filespec//​. If the //​[[CL:​Glossary:​file]]//​ is a //​[[CL:​Glossary:​source file]]// and the //​[[CL:​Glossary:​implementation]]//​ chooses to perform //​[[CL:​Glossary:​implicit compilation]]//,​ **load** must recognize //​[[CL:​Glossary:​top level forms]]// as described in {\secref\TopLevelForms} and arrange for each //​[[CL:​Glossary:​top level form]]// to be executed before beginning //​[[CL:​Glossary:​implicit compilation]]//​ of the next. (Note, however, that processing of **[[CL:​Special Operators:​eval-when]]** //​[[CL:​Glossary:​form|forms]]//​ by **load** is controlled by the **'':​execute''​** situation.)
 +If //verbose// is //​[[CL:​Glossary:​true]]//,​ **load** prints a message in the form of a comment (i.e. with a leading //​[[CL:​Glossary:​semicolon]]//​) to //​[[CL:​Glossary:​standard output]]// indicating what //​[[CL:​Glossary:​file]]//​ is being //​[[CL:​Glossary:​loaded]]//​ and other useful information. If //verbose// is //​[[CL:​Glossary:​false]]//,​ **load** does not print this information.
 +If //print// is //​[[CL:​Glossary:​true]]//,​ **load** incrementally prints information to //​[[CL:​Glossary:​standard output]]// showing the progress of the //​[[CL:​Glossary:​loading]]//​ process. For a //​[[CL:​Glossary:​source file]]//, this information might mean printing the //​[[CL:​Glossary:​values]]//​ //​[[CL:​Glossary:​yielded]]//​ by each //​[[CL:​Glossary:​form]]//​ in the //​[[CL:​Glossary:​file]]//​ as soon as those //​[[CL:​Glossary:​values]]//​ are returned. For a //​[[CL:​Glossary:​compiled file]]//, what is printed might not reflect precisely the contents of the //​[[CL:​Glossary:​source file]]//, but some information is generally printed. If //print// is //​[[CL:​Glossary:​false]]//,​ **load** does not print this information.
 +If the file named by //​filespec//​ is successfully loaded, **load** returns //​[[CL:​Glossary:​true]]//​. If the file does not exist, the specific action taken depends on //​if-does-not-exist//:​ if it is **[[CL:​Constant Variables:​nil]]**,​ **load** returns **[[CL:​Constant Variables:​nil]]**;​ otherwise, **load** signals an error.
 +The //​external-format//​ specifies the //​[[CL:​Glossary:​external file format]]// to be used when opening the //​[[CL:​Glossary:​file]]//​ (see the //​[[CL:​Glossary:​function]]//​ **[[CL:​Functions:​open]]**),​ except that when the //​[[CL:​Glossary:​file]]//​ named by //​filespec//​ is a //​[[CL:​Glossary:​compiled file]]//, the //​external-format//​ is ignored. **[[CL:​Functions:​compile-file]]** and **load** cooperate in an //​[[CL:​Glossary:​implementation-dependent]]//​ way to assure the preservation of the //​[[CL:​Glossary:​similarity]]//​ of //​[[CL:​Glossary:​characters]]//​ referred to in the //​[[CL:​Glossary:​source file]]// at the time the //​[[CL:​Glossary:​source file]]// was processed by the //​[[CL:​Glossary:​file compiler]]//​ under a given //​[[CL:​Glossary:​external file format]]//, regardless of the value of //​external-format//​ at the time the //​[[CL:​Glossary:​compiled file]]// is //​[[CL:​Glossary:​loaded]]//​.
 +**load** binds **[[CL:​Variables:​star-readtable-star|*readtable*]]** and **[[CL:​Variables:​star-package-star|*package*]]** to the values they held before //​[[CL:​Glossary:​loading]]//​ the file.
 +**[[CL:​Variables:​star-load-truename-star|*load-truename*]]** is //​[[CL:​Glossary:​bound]]//​ by **load** to hold the //​[[CL:​Glossary:​truename]]//​ of the //​[[CL:​Glossary:​pathname]]//​ of the file being //​[[CL:​Glossary:​loaded]]//​.
 +**[[CL:​Variables:​star-load-pathname-star|*load-pathname*]]** is //​[[CL:​Glossary:​bound]]//​ by **load** to hold a //​[[CL:​Glossary:​pathname]]//​ that represents //​filespec//​ merged against the defaults. That is, **[[CL:​Functions:​(pathname (merge-pathnames //​filespec//​))]]**.
 +In the below example, we establish a data file and then load it.
 +([[CL:​Macros:​with-open-file]] (str "​"​ :direction :​output ​
 +                               :​if-exists :​error) ​
 +  ([[CL:​Functions:​print]] 1 str) 
 +  ([[CL:​Functions:​print]] '​([[CL:​Macros:​defparameter]] a 888) str)
 +  [[CL:​Constant Variables:​t]]) <​r>​[[CL:​Constant Variables:​T]] </r>
 +(load "​"​) <​r>//​[[CL:​Glossary:​true]]//​ </r>
 +a <​r>​888 </r>
 +([[CL:​Macros:​defparameter]] *p* ([[CL:​Functions:​merge-pathnames]] "​"​)) <​r>​*P*</​r>​
 +(load *p* :verbose [[CL:​Constant Variables:​t]]) ​
 +<o>; Loading contents of file /​fred/​ ​
 +; Finished loading /​fred/​ </o>
 +<​r>//​[[CL:​Glossary:​true]]//​ </r>
 +(load p :print [[CL:​Constant Variables:​t]]) ​
 +<o>; Loading contents of file /​fred/​ ​
 +; 1 
 +; 888 
 +; Finished loading /​fred/​</​o> ​
 +<​r>//​[[CL:​Glossary:​true]]//​ </r>
 +;;; TODO make this example runnable
 +;;; ----[Begin file SETUP]---- ​
 +([[CL:​Macros:​in-package]] "​MY-STUFF"​) ​
 +([[CL:​Macros:​defmacro]] compile-truename () 
 +  `',​[[CL:​Variables:​star-compile-file-truename-star|*compile-file-truename*]]) <​r>​COMPILE-TRUENAME</​r>​
 +([[CL:​Macros:​defvar]] *my-compile-truename* ​
 +  (compile-truename) ​
 +  "Just for debugging."​)
 +([[CL:​Macros:​defvar]] *my-load-pathname* [[CL:​Variables:​star-load-pathname-star|*load-pathname*]]) ​
 +([[CL:​Macros:​defun]] load-my-system () 
 +  ([[CL:​Macros:​dolist]] (module-name '​("​FOO"​ "​BAR"​ "​BAZ"​)) ​
 +    (load ([[CL:​Functions:​merge-pathnames]] module-name *my-load-pathname*))))
 +;;; ----[End of file SETUP]----
 +(load "​SETUP"​) ​
 +(load-my-system) ​
 +====Affected By====
 +The implementation,​ and the host computer'​s file system.
 +====Exceptional Situations====
 +If **'':​if-does-not-exist''​** is supplied and is //​[[CL:​Glossary:​true]]//,​ or is not supplied, **load** signals an error of type **[[CL:​Types:​file-error]]** if the file named by //​filespec//​ does not exist,
 +or if the //​[[CL:​Glossary:​file system]]// cannot perform the requested operation.
 +An error of type **[[CL:​Types:​file-error]]** might be signaled if ''​([[CL:​Functions:​wild-pathname-p]] //​filespec//​)''​ returns //​[[CL:​Glossary:​true]]//​.
 +====See Also====
 +  * **[[CL:​Functions:​error|Function ERROR]]**
 +  * **[[CL:​Functions:​merge-pathnames|Function MERGE-PATHNAMES]]**
 +  * **[[CL:​Variables:​star-load-verbose-star|Variable *LOAD-VERBOSE*]]**
 +  * **[[CL:​Variables:​star-default-pathname-defaults-star|Variable *DEFAULT-PATHNAME-DEFAULTS*]]**
 +  * **[[CL:​Types:​pathname]]**
 +  * **[[CL:​Types:​logical-pathname]]**
 +  * {\secref\FileSystemConcepts}
 +  * {\secref\PathnamesAsFilenames}