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theory MyInduction
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imports Main
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begin
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fun itrev :: "'a list \<Rightarrow> 'a list \<Rightarrow> 'a list" where
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"itrev [] ys = ys" |
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"itrev (x#xs) ys = itrev xs (x#ys)"
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lemma "itrev xs [] = rev xs"
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apply(induction xs)
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apply(auto)
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oops
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lemma "itrev xs ys = rev xs @ ys"
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apply(induction xs arbitrary: ys)
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apply auto
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done
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