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Proof step 5 from proof perm-rmdup-rev (previous step)

a ∈ y, ∀ y. perm(x0, rmdup(rev(y))) ↔ perm(x0, rmdup(y)) ⊦ perm(x0, rmdup(rev(y) -l a)) ↔ perm(x0, rmdup(y) -1l a)

User applied rule insert rewrite lemma

And obtained the following new goals

Proof step 6:
⊦ rmdup(x) -1l a = rmdup(x -l a)
Proof step 7:
a ∈ y, ∀ y. perm(x0, rmdup(rev(y))) ↔ perm(x0, rmdup(y)) ⊦ perm(x0, rmdup(rev(y) -l a)) ↔ perm(x0, rmdup(y -l a))

Rule argument

spec: list-del inst: name: rmdup-del1-del seq: ⊦ rmdup(x) -1l a = rmdup(x -l a) subst: [a, x] → [a, y] flags: rewrite

Additional information

Used terms: a, y