- treplace mappingprocedure
The argument mapping is an association list (using equal? to compare keys), a hash-table, a one-argument procedure taking one argument and either producing that same argument or a replacement value, or another implementation-defined mapping object.
Returns a transducer which checks for the presence of any value passed through it in mapping. If a mapping is found, the value of that mapping is returned, otherwise it just returns the original value.
Must not keep any internal state. Modifying the mapping while it's in use by treplace is an error.