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Step * of Lemma mapfilter-as-reduce

∀[L,p,f:Top].  (mapfilter(λx.f[x];λx.p[x];L) ~ reduce(λx,a. if p[x] then [f[x] / a] else a fi ;[];L))
BY
{ (Unfold `mapfilter` 0 THEN ListIndSq `L' THEN RWO  "map-ifthenelse" 0 THEN Reduce 0 THEN Auto) }

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Latex:

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Latex:
\mforall{}[L,p,f:Top].    (mapfilter(\mlambda{}x.f[x];\mlambda{}x.p[x];L)  \msim{}  reduce(\mlambda{}x,a.  if  p[x]  then  [f[x]  /  a]  else  a  fi  ;[];L)\000C)


By

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Latex:
(Unfold  `mapfilter`  0  THEN  ListIndSq  `L'  THEN  RWO    "map-ifthenelse"  0  THEN  Reduce  0  THEN  Auto)

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