【发布时间】：2019-07-31 17:34:01
【问题描述】：
我正在尝试使用 C 中的 flex/bison 编写编程语言。但是，它在我的语法中报告了 117 个移位/减少冲突。其中，44 个来自表达式语法。我不明白为什么，因为我已经指定了优先级。
我已经尝试在我的野牛语法文件中添加优先规则：
%token INTEGER DOUBLE IDENTIFIER STRING RUNE TUPLEID
%token BEGIN END WHILE IF CLASS METHOD
%nonassoc BLOCKSTMT
%nonassoc ELSE
%nonassoc IFX
%right '=' INC DEC ASSIGN INCN DECN MULN DIVN MODN
%nonassoc ASSIGNBLOCK
%right STOP
%left GE LE EQ NE
%left '+' '-'
%left '*' '/' '%'
%nonassoc UMINUS
这并没有解决问题。我已经在 Stack Overflow 上查看了答案，但没有找到与我编写的语法类型相关的答案（这几乎只是从 yacc 教程扩展而来）。
expr:
INTEGER {
node_t *newInt = initNode(line, LEAFINT);
newInt->leaf.Integer = $1;
$$ = newInt;
}
| DOUBLE {
node_t *newDouble = initNode(line, LEAFDOUBLE);
newDouble->leaf.Double = $1;
$$ = newDouble;
}
| id { $$ = $1; }
| STRING {
node_t *newStr = initNode(line, LEAFSTRING);
newStr->leaf.String = $1;
$$ = newStr;
}
| RUNE {
node_t *newRune = initNode(line, LEAFRUNE);
if (strcmp($1, "\\n") == 0) {
newRune->leaf.Rune = '\n';
} else if (strcmp($1, "\\t") == 0) {
newRune->leaf.Rune = '\t';
} else if (strcmp($1, "\\\\") == 0) {
newRune->leaf.Rune = '\\';
} else if (strcmp($1, "\\'") == 0) {
newRune->leaf.Rune = '\'';
} else if (strlen($1) < 2) {
newRune->leaf.Rune = *$1;
} else {
yyerror("Error: Invalid rune literal.", line);
}
$$ = newRune;
}
| list { $$ = $1; }
| '-' expr %prec UMINUS {
node_t *negative = initNode(line, OPERATOR);
negative->operation = "-";
addOperand(negative, $2);
$$ = negative;
}
| expr '=' expr { $$ = binOpr(line, "=", $1, $3); }
| expr '+' expr { $$ = binOpr(line, "+", $1, $3); }
| expr '-' expr { $$ = binOpr(line, "-", $1, $3); }
| expr '*' expr { $$ = binOpr(line, "*", $1, $3); }
| expr '/' expr { $$ = binOpr(line, "/", $1, $3); }
| expr '%' expr { $$ = binOpr(line, "%", $1, $3); }
| expr EQ expr { $$ = binOpr(line, "==", $1, $3); }
| expr NE expr { $$ = binOpr(line, "!=", $1, $3); }
| expr '<' expr { $$ = binOpr(line, "<", $1, $3); }
| expr '>' expr { $$ = binOpr(line, ">", $1, $3); }
| expr LE expr { $$ = binOpr(line, "<=", $1, $3); }
| expr GE expr { $$ = binOpr(line, ">=", $1, $3); }
| expr INC {
node_t *increment = initNode(line, OPERATOR);
increment->operation = "++";
addOperand(increment, $1);
$$ = increment;
}
| INC expr {
node_t *increment = initNode(line, OPERATOR);
increment->operation = "++";
addOperand(increment, $2);
$$ = increment;
}
| expr DEC {
node_t *decrement = initNode(line, OPERATOR);
decrement->operation = "--";
addOperand(decrement, $1);
$$ = decrement;
}
| DEC expr {
node_t *decrement = initNode(line, OPERATOR);
decrement->operation = "--";
addOperand(decrement, $2);
$$ = decrement;
}
| expr INCN expr { $$ = binOpr(line, "+=", $1, $3); }
| expr DECN expr { $$ = binOpr(line, "-=", $1, $3); }
| expr MULN expr { $$ = binOpr(line, "*=", $1, $3); }
| expr DIVN expr { $$ = binOpr(line, "/=", $1, $3); }
| expr MODN expr { $$ = binOpr(line, "%=", $1, $3); }
| '(' expr ')' { $$ = $2 }
| expr STOP IDENTIFIER {
node_t *newID = initNode(line, LEAFID);
newID->leaf.Identifier = $3;
$$ = binOpr(line, ".", $1, newID);
}
| expr '[' expr ']' %prec STOP { $$ = binOpr(line, "index", $1, $3); }
| expr '(' expr ')' {
node_t *newList = initNode(line, LIST);
addOperand(newList, $3);
node_t *newCall = initNode(line, CALL);
addOperand(newCall, $1);
addOperand(newCall, newList);
$$ = newCall;
}
| expr parenlist {
node_t *newCall = initNode(line, CALL);
addOperand(newCall, $1);
addOperand(newCall, $2);
$$ = newCall;
}
我希望它能够正常编译我的编译器，但是当我执行“bison -d -v parse.y”时，它会给出警告“parse.y: warning: 117 shift/reduce conflict [-Wconflicts-sr ]。” y.output 文件内容如下：
State 122
40 expr: expr . '=' expr
41 | expr . '+' expr
42 | expr . '-' expr
43 | expr . '*' expr
44 | expr . '/' expr
45 | expr . '%' expr
46 | expr . EQ expr
47 | expr . NE expr
48 | expr . '<' expr
48 | expr '<' expr .
49 | expr . '>' expr
50 | expr . LE expr
51 | expr . GE expr
52 | expr . INC
54 | expr . DEC
56 | expr . INCN expr
57 | expr . DECN expr
58 | expr . MULN expr
59 | expr . DIVN expr
60 | expr . MODN expr
62 | expr . STOP IDENTIFIER
63 | expr . '[' expr ']'
64 | expr . '(' expr ')'
65 | expr . parenlist
'=' shift, and go to state 60
INC shift, and go to state 61
DEC shift, and go to state 62
INCN shift, and go to state 63
DECN shift, and go to state 64
MULN shift, and go to state 65
DIVN shift, and go to state 66
MODN shift, and go to state 67
STOP shift, and go to state 68
GE shift, and go to state 69
LE shift, and go to state 70
EQ shift, and go to state 71
NE shift, and go to state 72
'+' shift, and go to state 73
'-' shift, and go to state 74
'*' shift, and go to state 75
'/' shift, and go to state 76
'%' shift, and go to state 77
'(' shift, and go to state 79
'<' shift, and go to state 80
'>' shift, and go to state 81
'[' shift, and go to state 82
'=' [reduce using rule 48 (expr)]
INC [reduce using rule 48 (expr)]
DEC [reduce using rule 48 (expr)]
INCN [reduce using rule 48 (expr)]
DECN [reduce using rule 48 (expr)]
MULN [reduce using rule 48 (expr)]
DIVN [reduce using rule 48 (expr)]
MODN [reduce using rule 48 (expr)]
STOP [reduce using rule 48 (expr)]
GE [reduce using rule 48 (expr)]
LE [reduce using rule 48 (expr)]
EQ [reduce using rule 48 (expr)]
NE [reduce using rule 48 (expr)]
'+' [reduce using rule 48 (expr)]
'-' [reduce using rule 48 (expr)]
'*' [reduce using rule 48 (expr)]
'/' [reduce using rule 48 (expr)]
'%' [reduce using rule 48 (expr)]
'(' [reduce using rule 48 (expr)]
'<' [reduce using rule 48 (expr)]
'>' [reduce using rule 48 (expr)]
'[' [reduce using rule 48 (expr)]
$default reduce using rule 48 (expr)
parenlist go to state 83
arglist go to state 84
下一个状态，状态 123，似乎是相同的。状态 124 也是相同的，但没有冲突。
【问题讨论】：
标签： bison