A Fully Equational Proof of Parikh's Theorem
Luca Aceto, Zoltán Ésik, Anna Ingólfsdóttir (2010)
RAIRO - Theoretical Informatics and Applications
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We show that the validity of Parikh's theorem for context-free languages depends only on a few equational properties of least pre-fixed points. Moreover, we exhibit an infinite basis of -term equations of continuous commutative idempotent semirings.