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A general description is here.
The ‘@<-’ operator is now implemented as a primitive, which should reduce some copying of objects when used. Note that the operator object must now be in base: do not try to import it explicitly from package ‘methods’. Its validity test has been changed: previously it was that the slot name was part of the class definition: it is now that the slot already exists on the object.
‘sQuote()’ and ‘dQuote()’ now handle 0-length inputs. (Suggestion of