To check whether a particular feature is available, use the
#t if the specified feature is available, otherwise
To advertise a feature from your own Scheme code, you can use the
Add feature to the list of available features in this Guile process.
For C code, the equivalent function takes its feature name as a
char * argument for convenience:
(const char *str)¶
Add a symbol with name str to the list of available features in this Guile process.