User blog comment:Moooosey/Simple psi-- a fairly simple ocf/@comment-43798125-20191026225036/@comment-43798125-20191101235651

I was referring to the psi over the set C(a) = U (m<w) C_m(a)

In the definition, it's the function defined in the last line

C_m(a) = U (n<w) C_m,n(a)

psi_m(a) = min b|b not in C_m(a)

C(a) = U (m<w) C_m(a)

psi(a) = min b|b not in C(a)