我第一次广泛使用 Bison 语法。我有我的语法设置,和一个小测试套件来关联结果。
有时,测试套件会通过:
Reducing stack by rule 101 (line 613):
$1 = nterm mathenv ()
-> $$ = nterm closedTerm ()
Stack now 0 5 3
Entering state 120
Reading a token: Next token is token ENDMATH ()
Reducing stack by rule 28 (line 517):
$1 = nterm closedTerm ()
-> $$ = nterm compoundTerm ()
Stack now 0 5 3
Entering state 119
Reducing stack by rule 12 (line 333):
$1 = nterm compoundTerm ()
-> $$ = nterm compoundTermList ()
Stack now 0 5 3
Entering state 198
Next token is token ENDMATH ()
Shifting token ENDMATH ()
Entering state 325
... continues to completion ...
有时,它不会:
Reducing stack by rule 101 (line 613):
$1 = nterm mathenv ()
-> $$ = nterm closedTerm ()
Stack now 0 5 3
Entering state 120
Reading a token: Next token is token MN ()
Reducing stack by rule 28 (line 517):
$1 = nterm closedTerm ()
-> $$ = nterm compoundTerm ()
Stack now 0 5 3
Entering state 119
Reducing stack by rule 12 (line 333):
$1 = nterm compoundTerm ()
-> $$ = nterm compoundTermList ()
Stack now 0 5 3
Entering state 198
Next token is token MN ()
Shifting token MN ()
Entering state 11
... errors eventually ...
Now at end of input.
Line: 9 Error: syntax error at token
ENDMATH
是要转移到的正确标记,但有时MN
是确定的。每当我运行测试时,我都会得到不一致的结果。这种“随机”的歧义正常吗?可能是什么原因造成的?我应该定义一些%precedence
规则吗?
在y.output的顶部,我确实看到了一些状态冲突,例如
State 0 conflicts: 3 shift/reduce
State 120 conflicts: 2 shift/reduce
State 127 conflicts: 2 shift/reduce
State 129 conflicts: 2 shift/reduce
State 154 conflicts: 1 shift/reduce
State 207 conflicts: 3 shift/reduce
State 265 conflicts: 109 shift/reduce
State 266 conflicts: 109 shift/reduce
State 267 conflicts: 109 shift/reduce
State 268 conflicts: 109 shift/reduce
State 269 conflicts: 109 shift/reduce
State 342 conflicts: 2 shift/reduce
State 390 conflicts: 109 shift/reduce
State 391 conflicts: 109 shift/reduce
State 396 conflicts: 1 shift/reduce
State 397 conflicts: 1 shift/reduce
消除所有这些冲突是否可取?请注意,状态 120 被列为有冲突,并且是发生此随机错误之前的状态。