The third job; syntax tree, phrases, phrases directly Handles

1. Known grammar:

S->a|^|(T)

T->T,S|S

Analysis sentence (T, (^, a)), find all phrases, phrases and handle directly.

S=>(T)=>(T,S)=>(T,(T))=>(T,(T,S))=>(T,(S,S))=>(T,(^,S))=>(T,(^,a))

Syntax tree:

 

 

 All phrases: ^, a (^, a) T, (^, a) (T, (^, a)) ^ a

Direct phrases: ^ a

Handle: ^

 

2. The context-free grammar structure description language:

｛aⁿbⁿ|n>=0｝

｛a^mbⁿ|m>=n>=0｝

The if statement

(1) is provided grammar G (T): T-> ab | aTb | ε

if(n>0)

　　T->ab|aTb

else

　　T->ε

 

(2) disposed grammar G (T): T-> ab | a | aTb | ε

if(m>=n=0)

　　T->a|ε

else if(m>=n>0)

　　T->ab或T->aTb