1. understood that symbol string and set operations.
L={A,B, … ,Z,a,b, … ,z}
D={0,1, … ,9}
Description meaning under represented:
LUD: a collection of all the letters and numbers
LD: by the following set of strings of letters with numbers
L4: a set of strings of symbols of the four-letter
L *: symbol string set by all of the letters
D +: all symbols of one or several strings of digits set
L (LUD) *: it is in line with a set of strings beginning with the letter, followed by letters, digits
2. grammar G (Z): Z-> aZb | ab definition of what kind of language?
A: too meaning of the questions:
1、Z->aZb
2、Z->aZb，得 Z=>aZb=>a²Zb²...=>aⁿ﹣¹Zbⁿ﹣¹=>aⁿbⁿ
Therefore language L (G [Z]) = {aⁿbⁿ | n≥1}
3. Write grammar quaternion form materials 22 pages in Example 2.2 identifier (VN, VT, P, S).
A: I-> L | TL | TD
L->a|b|c|...|z
D->0|1|...|9
S=
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.
A: 1, i + i * i 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, i + i * i leftmost 推导:
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, i + (i + i) leftmost 推导:
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)