Question: Let PREFIX-FREE REX = {R| R is a regular expression and L(R) is prefix-free}. Show that PREFIX-FREEREX is decidable. Why does a similar approach fail

Let PREFIX-FREE_REX = {〈R〉| R is a regular expression and L(R) is prefix-free}. Show that PREFIX-FREEREX is decidable. Why does a similar approach fail to show that PREFIX FREE_CFG is decidable?

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