6.4.19 The Operator `-'
This operator may only be used in the following ways:
- record
-
symbol - This yields record without the attribute named symbol, if
symbol is an attribute name in record. If not, the
expression yields record.
- record
-
list - Here, list must be a list of symbols. This yields record
without the attributes in list.
- list
-
number - This yields list without the element at index number. If
this element does not exist, the expression yields list.
- list1
-
list2 - This yields the multi-set difference of the two lists list1 and
list2. This means, it yields the list list1, but the first
n appearances of each element will be deleted, if that element
appears n times in list2.
- number1
-
number2 - This yields the difference of number1 and number2.