Nuprl - Pf append_segment 1 1 1 1 1 1 1 1

1. T: Type
2. as: T*
3. i: {0...||as||}
4. j: {i...||as||}
5. k: {j...||as||}

ki (firstn(0;nth_tl(i;as)) @ firstn(-i+k;nth_tl(i;as))) = firstn(-i+k;nth_tl(i;as))

By: RWH (AddrC [2;1] (RecUnfoldC `firstn`)) 0 THEN Reduce 0

Generated subgoal:

1 ki ((Case of nth_tl(i;as); nil nil ; a.as' nil) @ firstn(-i+k;nth_tl(i;as))) = firstn(-i+k;nth_tl(i;as))

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