http://blog.gregwym.info/tag/parse/ http://blog.gregwym.info/lr-1--parser-example.html 2011-04-19T05:24:08+08:00 Terminal Symbols: 6个BOF, EOF, id, -, (, )Nonterminal Symbols: 3个S, expr, termStart Symbol:SProduction Rules: 5个 0 S BOF expr EOF 1 expr term 2 expr expr - term 3 term id 4 term ( expr ) Total State: 11个 (0 to 11)Total Transitions: 28个 State Symbol Action 0 BOF shift to state 6 1 ( shift to state 3 1 id shift to state 2 1 term shift to state 8 3 ( shift to state 3 3 expr shift to state 7 3 id shift to state 2 3 term shift to state 4 6 ( shift to state 3 6 expr shift to state 10 6 id shift to state 2 6 term shift to state 4 7 ) shift to state 9 7 - shift to state 1 10 - shift to state 1 10 EOF shift to state 5 2 ) reduce by rule 3 2 - reduce by rule 3 2 EOF reduce by rule 3 4 ) reduce by rule 1 4 - reduce by rule 1 4 EOF reduce by rule 1 8 ) reduce by rule 2 8 - reduce by rule 2 8 EOF reduce by rule 2 9 ) reduce by rule 4 9 - reduce by rule 4 9 EOF reduce by rule 4 String to Parse:BOF id - ( id ) - id EOFParse Step:蓝色的行是Shift, 灰色的行是ReduceReduce的次数取决于Production Rule RHS的长度当前Symbol所对应的State, State Stack (At EOL) Description S0 0 Start BOF S6 0 6 S0 BOF S6 id S2 0 6 2 S6 id S2 R3 - 0 6 S2 - Reduce by rule #3 (replace id with term) term S4 0 6 4 S6 term S4 R1 - 0 6 S4 - Reduce by rule #1 (replace term with expr) expr S10 0 6 10 S6 expr S10 - S1 0 6 10 1 S10 - S1 ( S3 0 6 10 1 3 S1 ( S3 id S2 0 6 10 1 3 2 S3 id S2 R3 ) 0 6 10 1 3 S2 ) Reduce by rule #3 (replace id with term) term S4 0 6 10 1 3 4 S3 term S4 R1 ) 0 6 10 1 3 S4 ) Reduce by rule #1 (replace term with expr) expr S7 0 6 10 1 3 7 S3 expr S7 ) S9 0 6 10 1 3 7 9 S7 ) S9 R4 R4 R4 - 0 6 10 1 S9 - Reduce by rule #4 (repace "( expr )" with term) term S8 0 6 10 1 8 S1 term S8 R2 R2 R2 - 0 6 S8 - Reduce by rule #2 (replace "expr - term" with expr) expr S10 0 6 10 S6 expr S10 - S1 0 6 10 1 S10 - S1 id S2 0 6 10 1 2 S1 id S2 R3 EOF 0 6 10 1 S2 EOF Reduce by rule #3 (replace id with term) term S8 0 6 10 1 8 S1 term S8 R2 R2 R2 EOF 0 6 S8 EOF Reduce by rule #2 (replace "expr - term" with expr) expr S10 0 6 10 S6 expr S10 EOF S5 Final S5 S10 EOF S5 原题来源: http://www.student.cs.uwaterloo.ca/~cs241/parsing/lr1.html