RACSO
R
DFA
CFG
Operations:
Reg
,
CF
PDA
Reductions:
K
,
WP
,
CFG
,
NP
,
SAT
ANTLR:
lex
,
syn
Exams
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Exercise
‹
10
›
:
Context-free description for
{
a
n
b
w
1
a
w
2
∣
w
1
,
w
2
∈
{
a
,
b
}
∗
∧
n
=
∣
w
2
∣
∧
∣
w
1
w
2
∣
a
a
a
=
0
∧
w
1
=
w
1
R
}
\{ a^nbw_1aw_2 \mid w_1,w_2\in\{a,b\}^*\;\wedge\;n=|w_2|\;\wedge\;|w_1w_2|_{aaa}=0\;\wedge\;w_1=w_1^R \}
{
a
n
b
w
1
a
w
2
∣
w
1
,
w
2
∈
{
a
,
b
}
∗
∧
n
=
∣
w
2
∣
∧
∣
w
1
w
2
∣
aaa
=
0
∧
w
1
=
w
1
R
}
Give a context-free description for the set of words of the form
a
n
b
w
1
a
w
2
a^nbw_1aw_2
a
n
b
w
1
a
w
2
such that
w
1
,
w
2
w_1,w_2
w
1
,
w
2
are constructed over the alphabet
{
a
,
b
}
\{a,b\}
{
a
,
b
}
, the size of
w
2
w_2
w
2
is
n
n
n
,
w
1
w
2
w_1w_2
w
1
w
2
has no occurrences of
a
a
a
aaa
aaa
, and the reverse of
w
1
w_1
w
1
is itself.
Authors:
Guillem Godoy /
Documentation:
main { // Write here your context-free description... }
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