Q ( ψ ψ ) ( x ) = x ψ ψ ( x ) = q ( x ) ψ ψ ( x ) , for each pointwisely defined square integrable class ψ ψ ∈ ∈ D Q and for each real number x, with domain D Q = { ψ ψ ∈ ∈ L 2 ( R ) ∣ ∣ q ψ ψ ∈ ∈ L 2 ( R ) } , where q : R → → C is the coordinate function sending each point x ∈ ∈ R to itself.