SCM provides user-definable datatypes with the same interface as SLIB, see See Records, with the following extension.
Causes records of type rtd to be printed in a user-specified format. rtd must be a record type descriptor returned by
make-record-type, printer a procedure accepting three arguments: the record to be printed, the port to print to, and a boolean which is true if the record is being written on behalf of
writeand false if for
display. If printer returns #f, the default record printer will be called.
A printer value of #f means use the default printer.
Only the default printer will be used when printing error messages.