1. understood that symbol string and set operations.
L={A,B, … ,Z,a,b, … ,z}
D={0,1, … ,9}
Description meaning under represented:
LUD represents a collection of all the letters and numbers .
LD represents a set of strings of all symbols consisting of a letter followed by a number of compositions .
L4 represented by the set of all strings of symbols of four letters .
L * is represented by all the letters of the symbol string comprising a set of null symbol strings .
D + represents a set of strings all symbols beginning with the letter, followed by letters, digits .
L (LUD) * represents all the symbols of one or several sets of strings of digits .
2. grammar G (Z): Z-> aZb | ab definition of what kind of language?
Z->aZb
Z->ab
Z->aZb->aaZbb->aaaZbbb->aaaaZbbbb->a...Zb...->a...b...
A n a number followed by the n b set of all strings of symbols.
3. Write grammar quaternion form materials 22 pages in Example 2.2 identifier (VN, NT, P, S).
Set I is the identifier, L letter, D is a number to give the title intended by
VN={I,L,D} VT={a,b,c,...,x,y,z,0,1,...,9}
P={ <I>-><L>
<I>-><I><L>
<I>-><I><D>
<L>->a
<L>->b
...
<L>->z
<D>->0
<D>->1
...
<D>->9 }
S=<I>
4. Write the following expressions leftmost derivation, rightmost derivation.
G (E):
E=> E + T | T
T=>T * F | F
F=>（E）| i
- i*i+i
- i+i*i
- i+(i+i)
Observe different leftmost and rightmost derivation process.
( 1 ) leftmost derivation :
E => E+T => T+T => T*F+T => F*F+T => i*F+T => i*i+T => i*i+F => i*i+i
Rightmost derivation :
E => E + T => E+F => E+i => T+i => T*F+i => T*i+i => F*i+i => i*i+i
( 2 ) the leftmost derivation :
E => E+T => T+T => F+T => i+T => i+T*F => i+F*F => i+i*F => i+i*i
Rightmost derivation :
E => E + T => E+T*F => E+T*i => E+F*i => E+i*i => T+i*i => F+i*i => i+i*i
( 3 ) leftmost derivation :
E=> E+T => T+T => F+T => i+T => i+F => i+(E) => i+(E+T) => i+(T+T) => i+(F+T) => i+(i+T) => i+(i+F) => i+(i+i)
Rightmost derivation :
E => E+T => E+F => E+(E) => E+(E+T) => E+(E+F) => E+(E+i) => E+(T+i) => E+(F+i) => E+(i+i) => T+(i+i) => F+(i+i) =>i+(i+i)