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clearer hypothesis of right-quotient dfa proof (#65)
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palmskog authored Nov 8, 2023
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6 changes: 3 additions & 3 deletions theories/dfa.v
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Expand Up @@ -306,7 +306,7 @@ Section RightQuotient.

Variable (A : dfa char).
Hypothesis acc_L1 : dfa_lang A =p L1.
Hypothesis dec_L2 : forall (q:A), decidable (exists2 y, L2 y & delta q y \in dfa_fin A).
Hypothesis dec_L2 : forall (q:A), decidable (exists2 y, L2 y & dfa_accept q y).

(** It would be better to not make the DFA explicit and require
decidabiliy of [(exists2 y, L2 y & L1 (x ++ y))] but that would
Expand All @@ -322,9 +322,9 @@ Section RightQuotient.
Proof using acc_L1.
apply: (iffP idP).
- rewrite inE /dfa_accept inE. case/dec_eq => y inL2.
rewrite -delta_cat => H. exists y => //. by rewrite -acc_L1.
rewrite /dfa_accept -delta_cat => H. exists y => //. by rewrite -acc_L1.
- case => y y1 y2. rewrite inE /dfa_accept inE /= dec_eq.
exists y => //. by rewrite -delta_cat acc_L1.
exists y => //. by rewrite /dfa_accept -delta_cat acc_L1.
Qed.

End RightQuotient.
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