RACSO
DFA
CFG
Operations:
Reg
,
CF
PDA
Reductions:
K
,
WP
,
CFG
,
NP
,
SAT
ANTLR:
lexical
,
syntactic
Exams
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Exercise
‹
18
›
:
{
g
∈
C
F
G
(
{
a
,
b
}
)
∣
L
(
g
)
=
{
a
,
b
}
∗
}
≤
{
G
∣
L
(
G
)
=
{
a
,
b
}
∗
−
{
a
b
}
}
\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{a,b\}^*-\{ab\}\}
{
g
∈
CFG
({
a
,
b
})
∣
L
(
g
)
=
{
a
,
b
}
∗
}
≤
{
G
∣
L
(
G
)
=
{
a
,
b
}
∗
−
{
ab
}}
Reduce the universality problem on CFGs over
{
a
,
b
}
\{a,b\}
{
a
,
b
}
to the problem of whether a CFG generates all words over
{
a
,
b
}
\{a,b\}
{
a
,
b
}
except the word
a
b
ab
ab
, in order to prove that such problem is not semi-decidable (not recursively enumerable).
Authors:
Carles Creus, Guillem Godoy /
Documentation:
input g { // Write your reduction here... // output ... ; }
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