Summary: 'C', is it's grammar context sensitive ?
John Lacey
john at basho.uucp
Sun Sep 2 11:20:02 AEST 1990
In article <1990Aug30.223440.7377 at NCoast.ORG> of comp.lang.c
ramsey at NCoast.ORG (Cedric Ramsey) writes:
} If you guys agree that 'C' is context sensitive then what languages
} truely are context-free, if any.
In article <11508 at crdgw1.crd.ge.com> of comp.lang.c
volpe at underdog.crd.ge.com (Christopher R Volpe) writes:
} Let's clarify some terminology here: First, all context free languages
} are context sensitive and all context free grammars are context sensitive.
} There is a hierarchy involved here. The concepts are not mutually
} exclusive, but rather the former is a superset of the latter. When you
} say "context sensitive", you really mean "non context free".
This seems hardly a clarification. You say all A are B and all B are A,
then claim there is a hierarchy in the next sentence.
There *is* a hierarchy. But "context sensitive" is not the same as
"non context free". The set of context-sensitive grammars is a superset
of the set of context-free grammars. This implies that all context-free
grammars are context-sensitive, but not all context-sensitive grammars
are context-free. The correct statement, then, is that C (as a complete
language) is context-sensitive but not context-free.
In brief, Chris said S <= F and F <= S and that C is ~F, when in fact,
F < S, and C is in (S - F). (All where F = context-free and
S = context-sensitive.)
Any further discussion on this topic belongs in comp.theory.
Toodles and cheers,
John
--
John Lacey,
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