In Larceny, file names generally follow Unix conventions, even on Windows. The following suffixes have special meanings to some components of Larceny.

.sls is the preferred suffix for files that consist of ERR5RS/R6RS-compatible library definitions.

.sch is the preferred suffix for files that contain R5RS source code.

.scm is an alternative suffix for files that contain R5RS source code.

.slfasl is the suffix for files that contain the pre-compiled form of ERR5RS/R6RS-compatible code.

.fasl is the suffix for files that contain the pre-compiled form of R5RS code.

.mal is the preferred suffix for files that contain MacScheme assembly language in symbolic form.

.lap is the suffix for files that contain MacScheme assembly language.

.lop is the suffix for files that contain machine code segments in the form expected by Larceny's heap linker.

.heap is the suffix for files that contain an executable heap image (must be combined with the larceny.bin runtime).

Larceny's root directory should contain the following files:

    larceny
    scheme-script
    larceny.bin
    larceny.heap
    startup.sch

The following subdirectories are also essential for correct operation of some features of some modes in some varieties of Larceny:

    include
    lib
    lib/Base
    lib/Debugger
    lib/Ffi
    lib/MzScheme
    lib/R6RS
    lib/SRFI
    lib/Standard
    lib/TeachPacks

The include subdirectory is used when compiling files with Petit Larceny.

The startup.sch file tells Larceny's require procedure to search some of the lib subdirectories for libraries that are loaded dynamically.

The R6RS does not specify any mapping from library names to files or to other locations at which the code for a library might be found. As R6RS non-normative appendix E puts it:

In other words, implementations are allowed to extend the R6RS with arbitrary mechanisms for resolving references to imported libraries, but R6RS programs that rely on such mechanisms are not portable. In particular, R6RS libraries are not portable.

Larceny provides five distinct Larceny-specific mechanisms that non-portable R6RS programs can use to import or to define libraries:

ERR5RS programs may use any of those five mechanisms, and may also use a sixth mechanism: An ERR5RS program can be written as a little configuration program that loads the program's libraries from files before any libraries are imported. This sixth mechanism is portable, but is not available to R6RS programs.

Suppose Larceny's -path option is used to specify a certain directory, and the program imports a nonstandard library whose name is of the form (name1 name2 … lastname). Larceny will search for that library in the following files:

The search starts with the first of those file names, continues with the following file names in order, and ends when a file with one of those names is found. The imported library must be one of the libraries defined within the first file found by this search, since the search is not continued after that first file is found (except as noted in the next paragraph).

If the search ends by finding a file whose name ends with .slfasl, then Larceny checks to see whether there is a file in the same directory with the same root name but ending with .sls instead of .slfasl. If the .sls file has been modified since the .slfasl file was last modified, then a warning is printed and the .sls file is loaded instead of the .slfasl file. Otherwise the .slfasl file is loaded.

In R5RS mode, Larceny's -path option and LARCENY_LIBPATH environment variable may be used to specify directories to be searched by the require procedure, which takes a single symbol libname as its argument. The require procedure will search for the following files in every directory that is part of the current require path, starting with the directories specified by LARCENY_LIBPATH and the -path option:

These files are expected to contain R5RS code, not library definitions. Otherwise the search proceeds much the same as when searching for an ERR5RS/R6RS library.

Procedure require

(require libname)

libname must be a symbol that names an R5RS-compatible library within the current require path.

If the library has not already been loaded, then it is located and loaded. If the library is found and loaded successfully, then require returns true; otherwise an error is signalled.

If the library has already been loaded, then require returns false without loading the library a second time.

Procedure current-require-path

(current-require-path ) => stringlist

(current-require-path stringlist)

The optional argument is a list of directory names (without slashes at the end) that should be searched by require and (in ERR5RS/R6RS modes) by Larceny's autoload feature. Returns the list of directory names that will be searched.