1
Ackermann = WF_Rel +
2
consts ack :: "nat * nat => nat"
3
recdef ack "measure(%m. m) ** measure(%n. n)"
4
"ack(0,n) = Suc n"
5
"ack(Suc m,0) = ack(m, 1)"
6
"ack(Suc m,Suc n) = ack(m,ack(Suc m,n))"
7
end