On Sun, Feb 24, 2013 at 10:04 PM, Tillmann Rendel < rendel@informatik.uni-marburg.de> wrote:
The recursion is well-founded if (drop n1 text) is smaller then text. So we have two cases, as Roman wrote:
If the language defined by B contains the empty string, then n1 can be 0, so the recursion is not well-founded and the parser might loop.
Ah! So "A ::= B A" is really /not/ the full grammar of the language but an abbreviated one, minus terminals. At the very least, partial parses make sense and the input stream is assumed finite. Because "A ::= B A" could be understood, not so much as a parsing rule, but as the full definition of a language which comprises only one word: BBBBB ... ad infinitum. So all that mention of well-foundedness was confusing. Thanks, Tillmann! -- Kim-Ee