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Dynamically Changing the PLT Search Path

Problem

You want to change the path where PLT searches for modules at runtime.

Solution

current-library-collection-paths will set the PLT library search path for you, based upon the list of strings you supply it. For example:

> (current-library-collection-paths 
   (append (current-library-collection-paths)
           '("d:\\source\\scheme\\schematics\\src\\libs")))

current-library-collection-paths with no arguments will return the current search path, so the append statement above has the effect of appending the given directory to the end of the collection search path.

Discussion

The library collection path is what is searched when you use a (require (lib ...)) statement. If you get an error standard-module-name-resolver: collection not found, you have a require that wasn't resolved. This technique works well when you're developing a collection that you don't want to install in the PLT search path just yet. There are a number of utilty functions that PLT provides for collections: find-library-collection-paths will tell you the current paths that PLT will search, but it's the initialized values, and is not affected by modifications done with current-library-collection-paths.

> (find-library-collection-paths)
("C:\\Documents and Settings\\gweakliem\\Application Data\\PLT Scheme\\207\\collects" 
"C:\\Program Files\\PLT\\collects")

collection-path will tell you what directory a given collection is loaded from:

> (collection-path "srfi")
"C:\\Program Files\\PLT\\collects\\srfi"

Comments about this recipe

Contributors

-- GordonWeakliem - 13 Aug 2004