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International Scholarly Research Notices
/
2012
/
Article
/
Auto 3
/
Research Article
An Application of Iterative Pushdown Automata to Contour Words of Balls and Truncated Balls in Hyperbolic Tessellations
Automaton 3
The 2-pushdown automaton recognizing the contour word of a truncated white sector in the pentagrid or in the heptagrid.
ββtwo states:
π
0
and
π
1
; input word in
{
π
,
π
,
π
,
π€
}
β
;
ββ
Ξ
=
{
π
,
π΅
,
π
,
π΅
π
,
π
π
,
π
π
,
π
,
πΉ
}
;
ββinitial state:
π
0
; initial stack:
π
[
π
]
; transition function
πΏ
:
ββ
πΏ
(
π
0
,
π
,
π
)
=
{
(
π
0
,
π
π’
π
β
2
(
πΉ
)
)
,
(
π
0
,
π
π’
π
β
1
(
π
π
)
)
}
ββ
πΏ
(
π
0
,
π
,
π
πΉ
)
=
{
(
π
0
,
π
π’
π
β
2
(
πΉ
πΉ
)
)
,
(
π
0
,
π
π’
π
β
1
(
π
π
)
)
}
ββ
πΏ
(
π
0
,
π
,
π
πΉ
)
=
(
π
1
,
π
π
π
2
)
;
πΏ
(
π
0
,
π
,
π΅
πΉ
)
=
(
π
1
,
π
π
π
2
)
ββ
πΏ
(
π
0
,
π
,
π
π
πΉ
)
=
(
π
1
,
π
π
π
2
)
;
πΏ
(
π
0
,
π
,
π
π
)
=
(
π
1
,
π
π
π
1
)
ββ
πΏ
(
π
0
,
π
,
π
π
πΉ
)
=
(
π
1
,
π
π
π
2
)
ββ
πΏ
(
π
0
,
π
,
π΅
π
πΉ
)
=
(
π
1
,
π
π
π
2
)
;
πΏ
(
π
0
,
π
,
π΅
π
)
=
(
π
0
,
π
π
π
1
)
;
πΏ
(
π
0
,
π
,
π΅
)
=
(
π
0
,
π
π
π
1
)
ββ
πΏ
(
π
0
,
π€
,
π
)
=
(
π
0
,
π
π
π
1
)
;
πΏ
(
π
0
,
π€
,
π
π
)
=
(
π
0
,
π
π
π
1
)
ββ
πΏ
(
π
0
,
π
,
π
πΉ
)
=
(
π
0
,
π
π
π
1
)
ββ
πΏ
(
π
1
,
π
,
π
π
πΉ
)
=
(
π
0
,
π
π’
π
β
1
(
π΅
π
π
π
π
)
)
;
πΏ
(
π
1
,
π
,
π
π
πΉ
)
=
(
π
0
,
π
π’
π
β
1
(
π΅
π
π
π
π
)
)
ββ
πΏ
(
π
1
,
π
,
π
πΉ
)
=
(
π
0
,
π
π’
π
β
1
(
π΅
π
π
)
)
ββ
πΏ
(
π
1
,
π
,
π΅
π
πΉ
)
=
(
π
0
,
π
π’
π
β
1
(
π΅
π
π
)
)
;
πΏ
(
π
1
,
π
,
π΅
πΉ
)
=
(
π
0
,
π
π’
π
β
1
(
π΅
π
)
)