The language supports set operators, logical operators, and value operators.
Set operators combine two set expressions or two transforms in different ways:
union operator combines all the elements of two sets. The following
transform will return all method calls or field references to members of a class:
set CallOrRefTransform to ( calls to methods in ) union ( references to fields in )
intersection operator creates a set containing only those elements that appear in both
operand sets. The following set expression will return calls to a class that come from methods in the class:
( calls to intersection calls from ) methods in class "ObjectDB"
without operator creates a set containing only those elements in the first operand
set that do not also exist in the second operand set. This operation is sometimes referred to as "difference".
The following set expression will return calls to class that come from methods outside the class:
( calls to without calls from ) methods in class "ObjectDB"
deintersection operator creates a set containing only those elements that appear
in one of the operand sets that don't appear in both operand sets. This operation is sometimes referred to as "symmetric difference".
Logical operators let you combine filters into different filters.
and operator results in a filter that passes a value only
if it passes both operand filters.
or operator results in a filter that passes a value if either
of the operand filters pass the value.
xor operator results in a filter that passes a value if either
of the operand filters, but not both, pass the value.
not operator applies to a single filter and
changes its sense, so that it rejects values it would pass and passes values
it would reject.
There are two kinds of operators that work only with value expressions: relational operators and value operators.
BBQ supports relational operators that compare two value expressions; the result of
the comparison is a filter. The
operators can compare any value expression type;
the relational operators
< <= >= >
can only compare values of type integer,
string, or date.
There is an additional relational operator
~= that produces a filter by
matching a string value
with a second string value interpreted as a Java regular expression. The following set expression
looks for strings that match "select", regardless of case:
to string ~= //(?i)select/ all strings
Value operators combine two value expressions into a single value expression.
BBQ currently defines only one value operator,
This operator concatenates two string-type expressions.
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