Terminator general capital letters, nonterminal generally lowercase letters
On BNF predetermined <terminator>, nonterminal
Leftmost derivation, rightmost derivation
Parse tree:
Ambiguous grammar:
Top-down analysis:
Correlation algorithm:
Look symbols to avoid backtracking before use.
Recursive descent analysis algorithm:
LL (1) analysis algorithm:
Grammar recursively go Chuzuo reextracted left common factor, please FIRST set, NULLABLE in sets, set FOLLOW
FIRST集：
FIRST set to be extended to an arbitrary string:
If LL (1) Analysis of the table there is a conflict does not belong grammar LL (1) grammar
FIRST set of the complete algorithm:
General calculation LL (1) analysis table Note:
NULLABLE集：
NULLABLE set calculation process:
FOLLOW set Calculated:
Seeking LL (1) Process analysis table: please FIRST set -----> ------- requirements set NULLABLE> ------- requirements set FOLLOW> Set request FIRST_S -> seeking LL ( 1) analysis table (might get conflicts)
Construction LL (1) analysis table:
For LL (1) syntax analysis LL (1) analysis table
Resolve conflicts LL (1) analysis table:
1, the elimination of left recursion, recursive and right turns
Eliminate indirect left recursion:
2, the left extracted common factor.
Bottom-up analysis, also known as Shift - reduce assay (the reverse process from top to bottom rightmost derivation):
Analysis steps:
