set-pp-type Show

flatten-module

binding-of 'nub
fix-intro ; def-rhs
split-2-beta nub [| absN |] [| repN |] ; assume

-- this bit to essentially undo the fix-intro
{ application-of 'repN ; app-arg ; let-intro 'nub ; one-td (unfold 'fix) ; simplify }
innermost let-float
alpha-let ['nub'] -- rename x to nub'

-- back to the derivation
binding-of 'worker
one-td (unfold 'repN)
remember origworker
one-td (unfold 'filter)
one-td (case-float-arg-lemma nubStrict)

-- prove strictness condition
lhs (unfold >>> undefined-expr)
end-proof

one-td (unfold 'nub')
simplify

one-td (case-float-arg-lemma nubStrict)
{ consider case ; consider case ; case-alt 1 ; alt-rhs
  unfold ; simplify
  one-td (unfold-rule "filter-fusion") ; assume
  simplify
  one-td (unfold-rule "member-fusion") ; assume
}
nonrec-to-rec
any-td (fold-remembered origworker)