A UnitMap is a unit (null) Mapping that has no effect on the coordinates supplied to it. They are simply copied. This can be useful if a Mapping is required (e.g. to pass to another function) but you do not want it to have any effect.
"format specifiers identified by
"symbols in the normal way.
"format specifiers, then an optional list of additional arguments may follow it in order to supply values to be substituted for these specifiers. The rules for supplying these are identical to those for the astSet function (and for the C
A null Object pointer (AST__NULL) will be returned if this function is invoked with the AST error status set, or if it should fail for any reason.