6.19.3 Require and provide

Special Form: require feature

If feature is not loaded, load it. Feature must be a string, and it is taken as a file name (without suffix) to be loaded. This loading takes place at compile time. The loaded file must provide feature; if not, a warning is issued.

If you load SLIB module, require is extended. See section 11.15 slib - SLIB interface for details.

Function: provide feature

Adds feature to the system's provided feature list, so that the subsequent require won't load the same file again. Usually this procedure should be called at the end of the Scheme file that is to be required. The reason that it should be at the end of file is that if an error is raised during loading, you may want to fix the error and require it again.

Function: provided? feature

Returns #t if feature is already provided.