doc-src/Tutorial/Misc/Fib.thy

theorem database now also indexes constants "Trueprop", "all",
"==>", "=="; thus thms_containing, findI etc. may retrieve more rules;

Fib = WF_Rel +
consts fib  :: nat => nat
recdef fib "measure(%n. n)"
    "fib 0 = 0"
    "fib 1 = 1"
    "fib (Suc(Suc x)) = fib x + fib (Suc x)"
end