Understanding of grammar and syntax jobs 02

1. understood that symbol string and set operations.

L={A,B, … ,Z,a,b, … ,z}

D={0,1, … ,9}

Description meaning under represented:

LUD: full set of letters and numbers

LD: the set of all strings of symbols consisting of a letter followed by a number composed of

L4: the set of all strings of symbols of the four-letter

L *: the set of all strings in the alphabet

D +: all symbols have one or several strings of digits set

The set of all strings beginning with the letter symbol, followed by the letter, numbers of: L (LUD) *

2. grammar G (Z): Z-> aZb | ab definition of what kind of language?

L（G）={aⁿbⁿ|n>1}

3. Write grammar quaternion form materials 22 pages in Example 2.2 identifier (VN, NT, P, S).

I-> l | IL | ID

L->a|b|c|...|x|y|z

D->0|1|...|8|9

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.

i*i+i
最左推导
E=>E+T=>T+T=>T*F+T=>F*F+T=>i*F+T=>i*i+T=>i*i+F=>i*i+i
最右推导
E=>E+T=>E+F=>E+i=>T+i=>T*F+i=>F*F+i=>i*F+i=>i*i+i

i+i*i
最左推导
E=>E+T=>T+T=>F+T=>i+T=>i+T*F=>i+F*F=>i+i*F=>i+i*i
最右推导
E=>E+T=>E+T=>E+T*F=>E+F*F=>E+i*F=>E+i*i=>T+i*i=>F+i*i=>i+i*i

i+(i+i)
最左推导
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)
最右推导
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)

Syntax tree