union

Usage

union(x,t)
union(x,y)
union!(x,t)
union!(x,y)

Signature

union:

(%, %) $\to$ %

Parameter	Type	Description
x,y	%	sets
t	T	an element

Returns

union(x,y) and union!(x,y) both return $x \cup y = \{ a \mbox{ such that }a \in x \mbox{ or } a \in y\}$, while union(x,t) and union!(x,t) both return $x \cup \{t\}$.

Remarks

union! does not make a copy of $x$, which is therefore modified after the call. It is unsafe to use the variable $x$ after the call, unless it has been assigned to the result of the call, as in x := union!(x, y).