@Section
   @Title { "@Next" }
   @Tag { next }
@Begin
@PP
next.sym @Index { @@Next symbol }
The @@Next symbol returns its parameter
plus one.  It is rather clever at working this out:  it hunts through
the parameter from right to left, looking for a number to increment:
@ID @Code {
"@Next (3.99)"
}
has result {@Next (3.99)}.  If @@Next cannot find a digit inside
its parameter, it is an error.  Roman numerals are handled by storing
them in a database, as explained in Section {@NumberOf paras};
@@Next will not increment a Roman numeral.
@End @Section