RACSO
R
DFA
CFG
Operations:
Reg
,
CF
PDA
Reductions:
K
,
WP
,
CFG
,
NP
,
SAT
ANTLR:
lex
,
syn
Exams
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Exercise
‹
11
›
:
Regular description for
σ
(
L
)
\sigma(L)
σ
(
L
)
where
L
=
{
w
∈
{
a
,
b
}
∗
∣
∃
x
,
y
:
(
w
=
x
a
y
∧
∣
y
∣
=
2
)
}
L=\{ w \in \{a,b\}^* \mid \exists x,y: (w=xay\;\wedge\;|y|=2) \}
L
=
{
w
∈
{
a
,
b
}
∗
∣
∃
x
,
y
:
(
w
=
x
a
y
∧
∣
y
∣
=
2
)}
and
σ
\sigma
σ
is the substitution defined by
σ
(
a
)
=
{
a
a
}
∗
\sigma(a)=\{aa\}^*
σ
(
a
)
=
{
aa
}
∗
and
σ
(
b
)
=
{
a
,
a
b
a
,
b
a
b
}
\sigma(b)=\{a,aba,bab\}
σ
(
b
)
=
{
a
,
aba
,
bab
}
Give a regular description for the image of the set of words over
{
a
,
b
}
\{a,b\}
{
a
,
b
}
, with an
a
a
a
in the third position starting from the end, through the substitution
σ
\sigma
σ
defined by
σ
(
a
)
=
{
a
a
}
∗
\sigma(a)=\{aa\}^*
σ
(
a
)
=
{
aa
}
∗
and
σ
(
b
)
=
{
a
,
a
b
a
,
b
a
b
}
\sigma(b)=\{a,aba,bab\}
σ
(
b
)
=
{
a
,
aba
,
bab
}
.
Authors:
Guillem Godoy /
Documentation:
main { // Write here your regular description... }
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