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Step * of Lemma length-concat

∀[ll:Top List List]. (||concat(ll)|| = l_sum(map(λl.||l||;ll)) ∈ ℤ)
BY
{ (Unfold `l_sum` 0
   THEN InductionOnList
   THEN (Reduce 0 THEN Auto)
   THEN RevHypSubst' (-1) 0
   THEN RWW "concat-cons length-append" 0
   THEN Auto) }

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Latex:

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Latex:
\mforall{}[ll:Top  List  List].  (||concat(ll)||  =  l\_sum(map(\mlambda{}l.||l||;ll)))


By

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Latex:
(Unfold  `l\_sum`  0
  THEN  InductionOnList
  THEN  (Reduce  0  THEN  Auto)
  THEN  RevHypSubst'  (-1)  0
  THEN  RWW  "concat-cons  length-append"  0
  THEN  Auto)

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