- mapping-adjoin mapping arg ...procedure
The mapping-adjoin procedure returns a newly allocated mapping that uses the same comparator as the mapping mapping and contains all the associations of mapping, and in addition new associations by processing the arguments from left to right. The args alternate between keys and values. Whenever there is a previous association for a key, the previous association prevails and the new association is skipped. It is an error to add an association to mapping whose key that does not return #t when passed to the type test procedure of the comparator.