
30 DISCRETE MATHEMATIC..._
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1.
The symbols 0 and 1 are in F.
2.
If
e and
e'
are in F then the expression (e
"e')
is in F.
3.
If
e and
e'
are in F then the expression ( e v e') is in
F.
4.
If
e is in F then the expression(---, e) is in
F.
5. F contains nothing else.
And here is one for binary trees.
Definition The set T
of
binary trees satisfies:
1.
A single node (just a dot) is in
T.
2.
If
t is in
T,
then the structure formed from
T,
a single new node and an arrow labeled "left" from the
new node to
t, is also in T.
3.
If
t is in
T,
then the structure formed from
t,
a single new node and an arrow labeled "right" ...