Step
*
1
2
of Lemma
max-of-intset
1. [P] : ℕ ─→ ℙ
2. ∀n:ℕ. Dec(P[n])@i
3. Dec(P[0])
⊢ (∀y:ℕ. ¬P[y] supposing y ≤ 0) ∨ (∃y:ℕ. ((y ≤ 0) ∧ P[y] ∧ (∀x:ℕ. ¬P[x] supposing y < x ∧ (x ≤ 0))))
BY
{ !two_place_expr{(, THENL ,)}((Unfold `decidable` -1 THEN D -1);((OrRight THENA Auto)
THEN (InstConcl [⌈0⌉])⋅
THEN Auto); ((OrLeft THENA Auto) THEN D 0 THEN Auto)
THEN !two_place_expr{(, THENL ,)}(Assert
⌈y = 0 ∈ ℤ⌉⋅;Auto; (HypSubst' -1 0
THEN Trivial
))) }
Latex:
1. [P] : \mBbbN{} {}\mrightarrow{} \mBbbP{}
2. \mforall{}n:\mBbbN{}. Dec(P[n])@i
3. Dec(P[0])
\mvdash{} (\mforall{}y:\mBbbN{}. \mneg{}P[y] supposing y \mleq{} 0) \mvee{} (\mexists{}y:\mBbbN{}. ((y \mleq{} 0) \mwedge{} P[y] \mwedge{} (\mforall{}x:\mBbbN{}. \mneg{}P[x] supposing y < x \mwedge{} (x \mleq{} 0))))
By
!two\_place\_expr\{(, THENL ,)\}((Unfold `decidable` -1 THEN D -1);
((OrRight THENA Auto)
THEN (InstConcl [\mkleeneopen{}0\mkleeneclose{}])\mcdot{}
THEN Auto); ((OrLeft THENA Auto) THEN D 0 THEN Auto)
THEN !two\_place\_expr\{(, THENL ,)\}(Assert \mkleeneopen{}y = 0\mkleeneclose{}\mcdot{};Auto; (HypSubst' -1 0
THEN Trivial
)))
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