2.4 Keywords

Keyword is a sequence of alphabetic characters and possibly some special characters. All keywords fall into two categories: reserved keywords, which cannot be used as symbolic names, and non-reserved keywords, which being recognized by context can be used as symbolic names.

Reserved keywords are the following:

and      else     mod      union
by       if       not      within
cross    in       or
diff     inter    symdiff
div      less     then

Non-reserved keywords are described in following sections.

All the keywords have fixed meaning, which will be explained on discussion of corresponding syntactic constructions, where the keywords are used.