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REF LIBRARY John Gibson, John Williams May 1991 Revised John Gibson Aug 1995 COPYRIGHT University of Sussex 1995. All Rights Reserved >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<<< >>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<<< POPLOG LIBRARY MECHANISMS >>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<<< >>>>>>>>>>>>>>>>>>>>>> <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Libraries are programs which provide much of Poplog's functionality. This REF file provides information on the Poplog library structure. where they are stored (including variable names), the rationale behind their storage, how they are found (using searchlists), and the procedures for manipulating these searchlists. Details are also given on the compilation procedures used for library files. CONTENTS - (Use <ENTER> g to access required sections) 1 Introduction 2 Types of Library 3 Library Directories 3.1 Note for VMS users 3.2 Standard Library Directories 4 Library Names and Library Search Lists 4.1 Search List Format 4.2 Standard Pop-11 Search Lists 4.3 Manipulating Search Lists 5 Locating Library Files: syssearchpath 6 Autoloading Pop-11 Library Files 7 Loading Library Files with uses 8 Loading Library Files Explicitly 9 Standard Library Directory Names --------------- 1 Introduction --------------- The term library denotes a program component, or set of program components, that can be handled as a single named entity. Much of Poplog's functionality is provided in library form. These libraries may be loaded into the core Poplog run-time system as desired. Poplog's libraries are stored in disk files, one library per file. It is not possible for one file to contain several libraries. The name of a library is the name of the file (as a string) which contains the library program. ------------------- 2 Types of Library ------------------- There are various types of library: (a) compile libraries (b) include libraries Compile libraries generally contain a single procedure definition, or a set of related procedure definitions. They are loaded into the run-time image by simply compiling the library file. Include libraries, on the other hand, consist of identifier declarations. When referenced, include libraries are not compiled: instead, their contents are merged into the current compiler input stream, as if the declarations were explicitly present in the current file. The term "include" is derived from C. Include libraries are documented fully in HELP * INCLUDE and REF * PROGLIST. Some libraries are autoloadable. These normally define a single identifier. Poplog will automatically load such libraries when that identifier is first referenced. The method by which this is accomplished is discussed below (and also in HELP * AUTOLOAD). Non-autoloadable libraries may define several related identifiers, and are only loaded on explicit request. ---------------------- 3 Library Directories ---------------------- Poplog's library files are divided amongst various library directories. Each directory groups libraries of a similar status. Roughly speaking, a library file is assigned to a particular library directory according to (a) subsystem (i.e. Pop-11, Prolog, Lisp or ML) (b) type (i.e. autoloadable, non-autoloadable, include) (c) function (e.g. X Windows Interface libraries, Ved libraries) 3.1 Note for VMS users ----------------------- In this file, directory names are specified in Unix format, which may be translated to VMS format as follows: UNIX VMS $usepop/pop/lib/auto/nl.p >> usepop:[pop.lib.auto]nl.p The section Filename Processing in REF * SYSUTIL discusses Unix to VMS filename translation in more detail. 3.2 Standard Library Directories --------------------------------- Poplog includes the following Pop-11 library directories: # pop/lib/auto # pop/lib/data # pop/lib/database # pop/lib/demo # pop/lib/flavours # pop/lib/include # pop/lib/lib # pop/lib/proto # pop/lib/sun # pop/lib/turtle # pop/lib/ved # pop/lib/ved/term # pop/x/pop/lib and these Lisp library directories: # pop/lisp/modules and these Prolog library directories: # pop/plog/auto # pop/plog/lib and these ML library directories: # pop/pml/lib The status and purpose of these libraries is discussed in DOC * SYSSPEC and HELP * LIBFILES. ----------------------------------------- 4 Library Names and Library Search Lists ----------------------------------------- Library names do not contain any directory information. Poplog therefore needs a mechanism for mapping library names to actual file pathnames. This mapping is effected using search lists. A search list specifies the set of directories in which to look for a particular library. Given a library name, and a search list, the procedure syssearchpath, will return the full library file pathname. The file HELP * SEARCH_LISTS provides a more tutorial introduction to this topic. Poplog documentation is also accessed via search lists. These are discussed in HELP * VEDSYSFILE and REF * VEDPROCS. 4.1 Search List Format ----------------------- Each element of a search list must be one of the following types of object: (a) string (b) list (c) word or identifier (d) procedure Strings denote explicit directory names (e.g. '$popautolib'). Lists are considered to be annotated directory names. They consist of a directory name (the first item in the list), plus additional information for use by the Poplog editor, Ved. Words and identifiers are treated as pointers to a "nested" search list. They may also be indirect references to strings or procedures. Procedures compute library file pathnames, given library names as argument. The manner in which syssearchpath uses these various types of search list component is discussed below. 4.2 Standard Pop-11 Search Lists --------------------------------- Pop-11 provides the following search lists as standard: popautolist -> search_list [variable] search_list -> popautolist The set of directories where Pop-11 autoloadable library files may be found. Its default value is the list: [ '$poplocalauto/' '$popautolib/' '$popvedlib/' '$popvedlib/term/' '$usepop/pop/lib/database/' ] Users may extend or modify this list; it is also extended by various system libraries (such as LIB * POPXLIB). See HELP * POPAUTOLIST. popuseslist -> search_list [variable] search_list -> popuseslist The set of Pop-11 library directories to be searched by the uses syntax construct. Its default value is the list: [ ^(ident popautolist) '$poplocal/local/lib/' '$popliblib/' '$popdatalib/' ] Users may extend or modify this list; it is also extended by various system libraries (such as LIB * POPXLIB). See HELP * POPUSESLIST. (Note that the use of 'ident popautolist' in the above means that the value of popautolist is not frozen into popuseslist, and changes to the former will be picked up in the latter.) popsyslist -> search_list [variable] search_list -> popsyslist This list is mainly used by the Popc compiler, and contains the set of all source and library directories to be searched for identifier declarations. Its default value is the list: [ '$usepop/pop/src/' '$usepop/pop/ved/src/' ^(ident popuseslist) ] Users may extend or modify this list; it is also extended by various system libraries (such as LIB * POPXLIB, which in addition to adding the X library directories to popuseslist also adds the X source directory $usepop/pop/x/src/ directly to popsyslist). (Note that the use of 'ident popuseslist' in the above means that the value of popuseslist is not frozen into popsyslist, and changes to the former will be picked up in the latter.) 4.3 Manipulating Search Lists ------------------------------ flatten_searchlist(search_list) -> list [procedure] flatten_searchlist(search_list, want_props) -> list Flattens a search list into a list of directory names (strings), i.e. dereferences any words or identifiers contained in search_list. If the optional argument want_props is supplied, and not false, then annotated directory names (2 or 3 element lists) are returned unchanged. Otherwise, annotated directory names are reduced to simple directory names. Note that flatten_searchlist cannot sensibly interpret procedures in a search list, so these are quietly ignored. extend_searchlist(item, search_list) -> search_list [procedure] extend_searchlist(item, search_list, at_end) -> search_list Adds item to the library search list search_list, unless it already contains item. item may be any valid search list component (i.e. a string, annotated directory name, word, identifier, or procedure). When testing whether item is a member of search_list, extend_searchlist dereferences pointers to nested search lists as necessary. If item needs to be added to search_list, it is added to the end of the list if the optional argument at_end is supplied and true; it is added to the front of the list otherwise. search_list is returned unchanged if it already contains item. ---------------------------------------- 5 Locating Library Files: syssearchpath ---------------------------------------- syssearchpath(search_list, lib_name) -> filename [procedure] syssearchpath(search_list, lib_name, bool) -> filename Searches the directories in search_list for the library named by lib_name, returning the full pathname of the file if successful, and false otherwise. syssearchpath examines the elements of search_list in left-to-right order, according to the algorithm described below (and also in HELP * SEARCH_LISTS): # If the element E is a string, it is considered to be a directory name. If a file called: sysfileok(E) dir_>< lib_name exists, then the search is terminated, and that filename is returned. Otherwise, if a directory named: sysfileok(E) dir_>< 'doc_index' exists, that directory is considered to be an index to the directory E. The procedure sys_search_doc_index (described in HELP * MKREFINDEX) is used to search the index for an entry for lib_name, as follows: sys_search_doc_index( lib_name, E, if bool then 2:01 else 2:11 endif) (bool is an optional argument, which defaults to false). If one or more index entries for lib_name are found, then: # If bool is false, or there is only one matching entry, the filename associated with lib_name by the index is returned. # If bool is true, and there is more than one matching entry, a vector containing the matching entries is returned. # If the element E is a procedure, it is applied to lib_name. The result, if non-false, is considered to be the full pathname of lib_name, and returned. # If the element E is a word or identifier, it is considered to be a pointer to a "nested" search list, which is examined recursively. # If the element E is a list, it is considered to be an annotated directory name. The head of the list may be a string, procedure, or word/identifier, and is processed as described in steps 1, 2, and 3 respectively. If this results in a pathname being determined, a copy of the list with the full pathname as its first element is returned. syssearchpath is used by vedsysfile (via vedgetlibfilename) to locate system documentation and library source code. ----------------------------------- 6 Autoloading Pop-11 Library Files ----------------------------------- The procedures and variables used to implemement Pop-11 autoloading are described below. For a more tutorial discussion, see HELP * AUTOLOAD. syslibcompile(lib_name, dir_list) -> dir [procedure] syslibcompile(lib_name) -> dir This procedure is used by sys_autoload to locate and compile Pop-11 library files. It searches the directories in dir_list for the library named by lib_name. If such a library is found, it is compiled (with pop11_compile), and the relevant directory is returned. Otherwise, syslibcompile returns false. The argument lib_name may be a string or a word. The file extension '.p' is added to lib_name if necessary. If the argument dir_list is omitted, popautolist is used. dir_list may contain the full range of search list components as described above. prautoloadwarn(lib_name) [procedure variable] Called by syslibcompile when it has determined the full pathname of the library named lib_name, immediately before compiling it. (Note that this only happens when lib_name is found in an actual directory, not when 'found' by a procedure in popautolist. Its default value is erase, which means that autoloading etc is normally done silently; the procedure sysprautoloadwarn may be assigned to this variable when notification is required. sysprautoloadwarn(lib_name) [procedure] This procedure may be assigned to prautoloadwarn when notification of autoloading is required. It prints the line ;;; AUTOLOADING lib_name on the standard output (i.e. through cucharout). sys_autoload(word) -> dir [procedure] This procedure is called by parts of the system that need to check that an autoloadable definition of a permanent identifier called WORD is loaded (e.g. see the description of macro expansion in REF * PROGLIST, and sysdeclare in REF * VMCODE). It first checks to see if word is already defined as a permanent identifier, and returns true if so. Here 'defined' means that isdefined(word) is true, i.e. that word has an attached identifier that is not just a 'weak' declaration (see REF * IDENT). If word is not defined, but pop_autoload is false, then false is returned. Otherwise, if pop_autoload is true, it tries to autoload word: If word has an autoloading procedure in the property sys_autoload_action, then that is called, i.e. if sys_autoload_action(word) -> P is a procedure, then P(word) -> dir Otherwise, the autoloading procedure defaults to syslibcompile(word) -> dir to try and autoload a file 'word.p' from one of the directories in popautolist. In either case, the result of the procedure is returned. It should normally be the case that an autoloading procedure/autoloaded file will define word as a permanent identifier; note that during the call of syslibcompile or the autoloading procedure, word is marked specially, so that a call of sys_autoload on the same word during compilation of the file will return false rather than cause a recursive call. In addition, an abnormal exit from sys_autoload during compilation will remove any declaration that word may have acquired (thus ensuring that word remains undefined after a compilation mishap). sys_autoload_action(word) -> p_or_false [procedure] p_or_false -> sys_autoload_action(word) Property used by sys_autoload. If word is to be autoloaded, and sys_autoload_action(word) -> p is a procedure, then that will be called instead of syslibcompile. (Note that whenever a given word becomes (strongly) declared as a permanent identifier, any sys_autoload_action for it is removed.) pop_autoload -> bool [variable] bool -> pop_autoload This variable (default value true) can be used to stop sys_autoload from autoloading undefined identifiers; when false, sys_autoload just returns false for such an identifier. Setting pop_autoload false is particularly useful for programs that wish to use itemread or nextitem to read words from proglist with macro expansion, but do not want undefined words to be autoloaded. ---------------------------------- 7 Loading Library Files with uses ---------------------------------- See HELP * USES for a description of the Pop-11 uses syntax construct. uses_lib_idents(lib_name, lib_list, id_names, flags) [procedure] System procedure called by the * uses syntax construct. useslib(lib_name) [procedure variable] This procedure was previously called by the uses syntax word. It is now the same as uses_lib_idents(lib_name, false, , 0) ----------------------------------- 8 Loading Library Files Explicitly ----------------------------------- The following procedures and syntax words are provided for loading library files explicitly. subsystem_libcompile(lib_name, dir_list) -> bool [procedure] Loads the library lib_name, using its file extension to determine to which subsystem the library belongs and hence which search-lists and which compiler to use. If a subsystem-specific version of the library cannot be found, the given dir_list is searched. The result indicates whether or not the library was found and compiled. loadlib(lib_name) [procedure variable] loadlib(lib_name, lib_list) Loads the library lib_name, by doing subsystem_libcompile(lib_name, lib_list) where lib_list defaults to popuseslist if not supplied as an optional second argument. An error is signalled if the library file cannot be found, i.e. if subsystem_libcompile returns false. (Note that subsystem_compile_warn is locally set to erase during this procedure.) syslibwarning(lib_name) [procedure] Uses sysprmessage to print a message of the form ;;; LOADING LIB lib_name syslibwarning is the default value of the procedure variable libwarning, a call to which is planted by the syntax word lib. libwarning(lib_name) [procedure variable] A call to this procedure is planted by the syntax word lib, in order to inform the user that the library lib_name is about to be compiled. The default value of libwarning is the procedure syslibwarning. ----------------------------------- 9 Standard Library Directory Names ----------------------------------- The following variables refer to standard Poplog library directories, via the environment variables (Unix) or logical names (VMS) defined in the file $popcom/popenv (Unix) or POPCOM:POPENV.COM (VMS). popdisk -> dir [variable] dir -> popdisk The root of the Poplog directory tree. Default value '$usepop/' (Unix) or 'usepop:' (VMS). This variable is only used at system- build time; altering its value has no effect whatsoever. poplibdir -> dir [variable] dir -> poplibdir The main Pop-11 autoloadable library directory. Default value '$popautolib/' (Unix) or 'popautolib:' (VMS). This variable is only used at system-build time; altering its value has no effect whatsoever. vedlibdir -> dir [variable] dir -> vedlibdir The main Ved autoloadable library directory. Default value '$popvedlib/' (Unix) or 'popvedlib:' (VMS). This variable is only used at system-build time; altering its value has no effect whatsoever. popliblibdir -> dir [variable] dir -> popliblibdir The main Pop-11 non autoloadable library directory. Default value '$popliblib/' (Unix) or 'popliblib:' (VMS). The value of this variable is inserted into popuseslist when that list is first created, after which, altering its value has no effect whatsoever. popdatalib -> dir [variable] dir -> popdatalib A Pop-11 library directory, containing miscellaneous data used by other library programs. Default value '$popdatalib/' (Unix) or 'popdatalib:' (VMS). The value of this variable is inserted into popuseslist when that list is first created, after which, altering its value has no effect whatsoever. popsunlib -> dir [variable] dir -> popsunlib The library directory where SUN-specific Pop-11 software is kept. Default value is '$popsunlib/' (Unix) or 'popsunlib:' (VMS). This variable is only defined if running on a SUN, in which case its value is included in popautolist (and therefore popuseslist). To define popsunlib on a machine other than a SUN, load LIB * POPSUNLIB. (Default value '$popsunlib/' ). popturtlelib -> dir [variable] dir -> popturtlelib This variable is only defined if the library LIB * POPTURTLELIB has been loaded. It holds the library directory used by the Pop-11 "turtle" graphics package. Its default value is '$usepop/pop/lib/turtle/' (Unix) or USEPOP:[POP.LIB.TURTLE] (VMS). Loading LIB * POPTURTLELIB adds popturtlelib to the end of popautolist. --- C.all/ref/library --- Copyright University of Sussex 1995. All rights reserved.