Talk:String operations

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String substitution

What does this mean? An example of string substitution occurs in regular languages, which are closed under string substitution. That is, if the letters of a regular language are substituted by other regular languages, the result is still a regular language. What is the reference? Deltahedron (talk) 21:05, 22 March 2013 (UTC)[reply]

I'll think about an example for that. Meanwhile, I hope that the examples I added are helpful and not too trivial.

Another question: aren't regular (string) languages also closed w.r.t. inverse string homomorphisms? The TATA-Book (reference see Regular_tree_grammar#External_links) says, even regular tree languages are. However, I didn't check whether its notion of inverse homomorphism its similar to the one here. Jochen Burghardt (talk) 15:52, 25 May 2013 (UTC)[reply]