Operations on Sets

Some of the operators that are used for bitwise operations (|, & and ^) can also be used for operations on sets, such as union and intersection. They can be applied to multisets, but also to arrays and mappings.

Operation	Syntax	Result
Intersection (and)	a & b	All elements present in both a and b.
Union (or)	a | b	All elements present in at least one of a and b.
Symmetric difference (exclusive or)	a ^ b	All elements present in a or b, but not present in both.

Two calculate the difference between two multisets, arrays or mappings, you use the - operator:

Operation	Syntax	Result
difference	a - b	All elements present in a, but not in b.

When using mappings in set operations, we only consider the indices. The values are copied along with the indices. If an index is present in both mappings in a union or intersection, the one from the right-side mapping will be used.

Some examples:

mapping m1 = ([ 1:"one", 2:"two" ]),
        m2 = ([ 2:"TWO", 3:"THREE" ]);

Expression	Result
m1 & m2	([ 2:"TWO" ])
m1 | m2	([ 1:"one", 2:"TWO", 3:"THREE" ])
m1 + m2	([ 1:"one", 2:"TWO", 3:"THREE" ])
m1 ^ m2	([ 1:"one", 3:"THREE" ])
m1 - m2	([ 1:"one" ])

You can also use the operator + on multisets, arrays and mappings. For multisets and mappings, it calculates the union, i e the same as the | operator. For arrays, it gives a different result: it just concatenates the arrays, instead of calculating the union:

Expression	Result
({ 1, 2, 4 }) | ({ 3, 4 })	({ 1, 2, 3, 4 })
({ 1, 2, 4 }) + ({ 3, 4 })	({ 1, 2, 4, 3, 4 })