TY - JOUR
T1 - Some inherently ambiguous context-free languages
AU - Shamir, Eliahu
PY - 1971/5
Y1 - 1971/5
N2 - We prove the inherent ambiguity of certain context-free languages, the prototype of which is L = {s 2 t | t = υ′ over(s, -) υ, s, υ, υ′ ∈ {0, 1}*} , (over(s,-) is the reflection of s). Actually, we prove that in general the degree of ambiguity of ent is, as expected, at least the number of factorizations t = υ′ over(s, -) υ. We also prove inherent direct ambiguity (of infinite degree) of certain languages, and the recursive unsolvability of that property.
AB - We prove the inherent ambiguity of certain context-free languages, the prototype of which is L = {s 2 t | t = υ′ over(s, -) υ, s, υ, υ′ ∈ {0, 1}*} , (over(s,-) is the reflection of s). Actually, we prove that in general the degree of ambiguity of ent is, as expected, at least the number of factorizations t = υ′ over(s, -) υ. We also prove inherent direct ambiguity (of infinite degree) of certain languages, and the recursive unsolvability of that property.
UR - http://www.scopus.com/inward/record.url?scp=0015064136&partnerID=8YFLogxK
U2 - 10.1016/S0019-9958(71)90455-4
DO - 10.1016/S0019-9958(71)90455-4
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AN - SCOPUS:0015064136
SN - 0019-9958
VL - 18
SP - 355
EP - 363
JO - Information and control
JF - Information and control
IS - 4
ER -