问题
I'm having an issue with my bison grammar, it is giving me shift/reduce errors, and I have already defined precedence for the operators.
I know that it is cause by the 'expr binop expr' bit of the expr rule. Here is my bison file, and the output I get. Any help would be very much appreciated.
%token ID KEYWORD INTCON FLOATCON TYPE STRING
%token IF WHILE FOR VOID RETURN
%token AND_OP OR_OP EQ_OP NEQ_OP LEQ_OP GEQ_OP
%left OR_OP
%left AND_OP
%nonassoc '<' LEQ_OP '>' GEQ_OP EQ_OP NEQ_OP
%left '+' '-'
%left '/' '*'
%right '!'
%%
expr : unop expr
| expr binop expr
| ID
| ID '[' expr ']'
| ID '(' expr_list ')'
| ID '(' ')'
| '(' expr ')'
| INTCON
| FLOATCON
;
expr_list : expr
| expr_list ',' expr
;
unop : '!' ;
binop : AND_OP | OR_OP | EQ_OP | NEQ_OP | '+' | '-' | '*' | '/' | LEQ_OP | '<' | GEQ_OP | '>' ;
And the output file:
Terminals unused in grammar
KEYWORD
TYPE
STRING
IF
WHILE
FOR
VOID
RETURN
State 25 conflicts: 12 shift/reduce
State 31 conflicts: 12 shift/reduce
Grammar
0 $accept: expr $end
1 expr: unop expr
2 | expr binop expr
3 | ID
4 | ID '[' expr ']'
5 | ID '(' expr_list ')'
6 | ID '(' ')'
7 | '(' expr ')'
8 | INTCON
9 | FLOATCON
10 expr_list: expr
11 | expr_list ',' expr
12 unop: '!'
13 binop: AND_OP
14 | OR_OP
15 | EQ_OP
16 | NEQ_OP
17 | '+'
18 | '-'
19 | '*'
20 | '/'
21 | LEQ_OP
22 | '<'
23 | GEQ_OP
24 | '>'
Terminals, with rules where they appear
$end (0) 0
'!' (33) 12
'(' (40) 5 6 7
')' (41) 5 6 7
'*' (42) 19
'+' (43) 17
',' (44) 11
'-' (45) 18
'/' (47) 20
'<' (60) 22
'>' (62) 24
'[' (91) 4
']' (93) 4
error (256)
ID (258) 3 4 5 6
KEYWORD (259)
INTCON (260) 8
FLOATCON (261) 9
TYPE (262)
STRING (263)
IF (264)
WHILE (265)
FOR (266)
VOID (267)
RETURN (268)
AND_OP (269) 13
OR_OP (270) 14
EQ_OP (271) 15
NEQ_OP (272) 16
LEQ_OP (273) 21
GEQ_OP (274) 23
Nonterminals, with rules where they appear
$accept (32)
on left: 0
expr (33)
on left: 1 2 3 4 5 6 7 8 9, on right: 0 1 2 4 7 10 11
expr_list (34)
on left: 10 11, on right: 5 11
unop (35)
on left: 12, on right: 1
binop (36)
on left: 13 14 15 16 17 18 19 20 21 22 23 24, on right: 2
state 0
0 $accept: . expr $end
1 expr: . unop expr
2 | . expr binop expr
3 | . ID
4 | . ID '[' expr ']'
5 | . ID '(' expr_list ')'
6 | . ID '(' ')'
7 | . '(' expr ')'
8 | . INTCON
9 | . FLOATCON
12 unop: . '!'
ID shift, and go to state 1
INTCON shift, and go to state 2
FLOATCON shift, and go to state 3
'!' shift, and go to state 4
'(' shift, and go to state 5
expr go to state 6
unop go to state 7
state 1
3 expr: ID . [$end, AND_OP, OR_OP, EQ_OP, NEQ_OP, LEQ_OP, GEQ_OP, '<', '>', '+', '-', '/', '*', ']', ')', ',']
4 | ID . '[' expr ']'
5 | ID . '(' expr_list ')'
6 | ID . '(' ')'
'(' shift, and go to state 8
'[' shift, and go to state 9
$default reduce using rule 3 (expr)
state 2
8 expr: INTCON .
$default reduce using rule 8 (expr)
state 3
9 expr: FLOATCON .
$default reduce using rule 9 (expr)
state 4
12 unop: '!' .
$default reduce using rule 12 (unop)
state 5
1 expr: . unop expr
2 | . expr binop expr
3 | . ID
4 | . ID '[' expr ']'
5 | . ID '(' expr_list ')'
6 | . ID '(' ')'
7 | . '(' expr ')'
7 | '(' . expr ')'
8 | . INTCON
9 | . FLOATCON
12 unop: . '!'
ID shift, and go to state 1
INTCON shift, and go to state 2
FLOATCON shift, and go to state 3
'!' shift, and go to state 4
'(' shift, and go to state 5
expr go to state 10
unop go to state 7
state 6
0 $accept: expr . $end
2 expr: expr . binop expr
13 binop: . AND_OP
14 | . OR_OP
15 | . EQ_OP
16 | . NEQ_OP
17 | . '+'
18 | . '-'
19 | . '*'
20 | . '/'
21 | . LEQ_OP
22 | . '<'
23 | . GEQ_OP
24 | . '>'
$end shift, and go to state 11
AND_OP shift, and go to state 12
OR_OP shift, and go to state 13
EQ_OP shift, and go to state 14
NEQ_OP shift, and go to state 15
LEQ_OP shift, and go to state 16
GEQ_OP shift, and go to state 17
'<' shift, and go to state 18
'>' shift, and go to state 19
'+' shift, and go to state 20
'-' shift, and go to state 21
'/' shift, and go to state 22
'*' shift, and go to state 23
binop go to state 24
state 7
1 expr: . unop expr
1 | unop . expr
2 | . expr binop expr
3 | . ID
4 | . ID '[' expr ']'
5 | . ID '(' expr_list ')'
6 | . ID '(' ')'
7 | . '(' expr ')'
8 | . INTCON
9 | . FLOATCON
12 unop: . '!'
ID shift, and go to state 1
INTCON shift, and go to state 2
FLOATCON shift, and go to state 3
'!' shift, and go to state 4
'(' shift, and go to state 5
expr go to state 25
unop go to state 7
state 8
1 expr: . unop expr
2 | . expr binop expr
3 | . ID
4 | . ID '[' expr ']'
5 | . ID '(' expr_list ')'
5 | ID '(' . expr_list ')'
6 | . ID '(' ')'
6 | ID '(' . ')'
7 | . '(' expr ')'
8 | . INTCON
9 | . FLOATCON
10 expr_list: . expr
11 | . expr_list ',' expr
12 unop: . '!'
ID shift, and go to state 1
INTCON shift, and go to state 2
FLOATCON shift, and go to state 3
'!' shift, and go to state 4
'(' shift, and go to state 5
')' shift, and go to state 26
expr go to state 27
expr_list go to state 28
unop go to state 7
state 9
1 expr: . unop expr
2 | . expr binop expr
3 | . ID
4 | . ID '[' expr ']'
4 | ID '[' . expr ']'
5 | . ID '(' expr_list ')'
6 | . ID '(' ')'
7 | . '(' expr ')'
8 | . INTCON
9 | . FLOATCON
12 unop: . '!'
ID shift, and go to state 1
INTCON shift, and go to state 2
FLOATCON shift, and go to state 3
'!' shift, and go to state 4
'(' shift, and go to state 5
expr go to state 29
unop go to state 7
state 10
2 expr: expr . binop expr
7 | '(' expr . ')'
13 binop: . AND_OP
14 | . OR_OP
15 | . EQ_OP
16 | . NEQ_OP
17 | . '+'
18 | . '-'
19 | . '*'
20 | . '/'
21 | . LEQ_OP
22 | . '<'
23 | . GEQ_OP
24 | . '>'
AND_OP shift, and go to state 12
OR_OP shift, and go to state 13
EQ_OP shift, and go to state 14
NEQ_OP shift, and go to state 15
LEQ_OP shift, and go to state 16
GEQ_OP shift, and go to state 17
'<' shift, and go to state 18
'>' shift, and go to state 19
'+' shift, and go to state 20
'-' shift, and go to state 21
'/' shift, and go to state 22
'*' shift, and go to state 23
')' shift, and go to state 30
binop go to state 24
state 11
0 $accept: expr $end .
$default accept
state 12
13 binop: AND_OP .
$default reduce using rule 13 (binop)
state 13
14 binop: OR_OP .
$default reduce using rule 14 (binop)
state 14
15 binop: EQ_OP .
$default reduce using rule 15 (binop)
state 15
16 binop: NEQ_OP .
$default reduce using rule 16 (binop)
state 16
21 binop: LEQ_OP .
$default reduce using rule 21 (binop)
state 17
23 binop: GEQ_OP .
$default reduce using rule 23 (binop)
state 18
22 binop: '<' .
$default reduce using rule 22 (binop)
state 19
24 binop: '>' .
$default reduce using rule 24 (binop)
state 20
17 binop: '+' .
$default reduce using rule 17 (binop)
state 21
18 binop: '-' .
$default reduce using rule 18 (binop)
state 22
20 binop: '/' .
$default reduce using rule 20 (binop)
state 23
19 binop: '*' .
$default reduce using rule 19 (binop)
state 24
1 expr: . unop expr
2 | . expr binop expr
2 | expr binop . expr
3 | . ID
4 | . ID '[' expr ']'
5 | . ID '(' expr_list ')'
6 | . ID '(' ')'
7 | . '(' expr ')'
8 | . INTCON
9 | . FLOATCON
12 unop: . '!'
ID shift, and go to state 1
INTCON shift, and go to state 2
FLOATCON shift, and go to state 3
'!' shift, and go to state 4
'(' shift, and go to state 5
expr go to state 31
unop go to state 7
state 25
1 expr: unop expr . [$end, AND_OP, OR_OP, EQ_OP, NEQ_OP, LEQ_OP, GEQ_OP, '<', '>', '+', '-', '/', '*', ']', ')', ',']
2 | expr . binop expr
13 binop: . AND_OP
14 | . OR_OP
15 | . EQ_OP
16 | . NEQ_OP
17 | . '+'
18 | . '-'
19 | . '*'
20 | . '/'
21 | . LEQ_OP
22 | . '<'
23 | . GEQ_OP
24 | . '>'
AND_OP shift, and go to state 12
OR_OP shift, and go to state 13
EQ_OP shift, and go to state 14
NEQ_OP shift, and go to state 15
LEQ_OP shift, and go to state 16
GEQ_OP shift, and go to state 17
'<' shift, and go to state 18
'>' shift, and go to state 19
'+' shift, and go to state 20
'-' shift, and go to state 21
'/' shift, and go to state 22
'*' shift, and go to state 23
AND_OP [reduce using rule 1 (expr)]
OR_OP [reduce using rule 1 (expr)]
EQ_OP [reduce using rule 1 (expr)]
NEQ_OP [reduce using rule 1 (expr)]
LEQ_OP [reduce using rule 1 (expr)]
GEQ_OP [reduce using rule 1 (expr)]
'<' [reduce using rule 1 (expr)]
'>' [reduce using rule 1 (expr)]
'+' [reduce using rule 1 (expr)]
'-' [reduce using rule 1 (expr)]
'/' [reduce using rule 1 (expr)]
'*' [reduce using rule 1 (expr)]
$default reduce using rule 1 (expr)
binop go to state 24
state 26
6 expr: ID '(' ')' .
$default reduce using rule 6 (expr)
state 27
2 expr: expr . binop expr
10 expr_list: expr . [')', ',']
13 binop: . AND_OP
14 | . OR_OP
15 | . EQ_OP
16 | . NEQ_OP
17 | . '+'
18 | . '-'
19 | . '*'
20 | . '/'
21 | . LEQ_OP
22 | . '<'
23 | . GEQ_OP
24 | . '>'
AND_OP shift, and go to state 12
OR_OP shift, and go to state 13
EQ_OP shift, and go to state 14
NEQ_OP shift, and go to state 15
LEQ_OP shift, and go to state 16
GEQ_OP shift, and go to state 17
'<' shift, and go to state 18
'>' shift, and go to state 19
'+' shift, and go to state 20
'-' shift, and go to state 21
'/' shift, and go to state 22
'*' shift, and go to state 23
$default reduce using rule 10 (expr_list)
binop go to state 24
state 28
5 expr: ID '(' expr_list . ')'
11 expr_list: expr_list . ',' expr
')' shift, and go to state 32
',' shift, and go to state 33
state 29
2 expr: expr . binop expr
4 | ID '[' expr . ']'
13 binop: . AND_OP
14 | . OR_OP
15 | . EQ_OP
16 | . NEQ_OP
17 | . '+'
18 | . '-'
19 | . '*'
20 | . '/'
21 | . LEQ_OP
22 | . '<'
23 | . GEQ_OP
24 | . '>'
AND_OP shift, and go to state 12
OR_OP shift, and go to state 13
EQ_OP shift, and go to state 14
NEQ_OP shift, and go to state 15
LEQ_OP shift, and go to state 16
GEQ_OP shift, and go to state 17
'<' shift, and go to state 18
'>' shift, and go to state 19
'+' shift, and go to state 20
'-' shift, and go to state 21
'/' shift, and go to state 22
'*' shift, and go to state 23
']' shift, and go to state 34
binop go to state 24
state 30
7 expr: '(' expr ')' .
$default reduce using rule 7 (expr)
state 31
2 expr: expr . binop expr
2 | expr binop expr . [$end, AND_OP, OR_OP, EQ_OP, NEQ_OP, LEQ_OP, GEQ_OP, '<', '>', '+', '-', '/', '*', ']', ')', ',']
13 binop: . AND_OP
14 | . OR_OP
15 | . EQ_OP
16 | . NEQ_OP
17 | . '+'
18 | . '-'
19 | . '*'
20 | . '/'
21 | . LEQ_OP
22 | . '<'
23 | . GEQ_OP
24 | . '>'
AND_OP shift, and go to state 12
OR_OP shift, and go to state 13
EQ_OP shift, and go to state 14
NEQ_OP shift, and go to state 15
LEQ_OP shift, and go to state 16
GEQ_OP shift, and go to state 17
'<' shift, and go to state 18
'>' shift, and go to state 19
'+' shift, and go to state 20
'-' shift, and go to state 21
'/' shift, and go to state 22
'*' shift, and go to state 23
AND_OP [reduce using rule 2 (expr)]
OR_OP [reduce using rule 2 (expr)]
EQ_OP [reduce using rule 2 (expr)]
NEQ_OP [reduce using rule 2 (expr)]
LEQ_OP [reduce using rule 2 (expr)]
GEQ_OP [reduce using rule 2 (expr)]
'<' [reduce using rule 2 (expr)]
'>' [reduce using rule 2 (expr)]
'+' [reduce using rule 2 (expr)]
'-' [reduce using rule 2 (expr)]
'/' [reduce using rule 2 (expr)]
'*' [reduce using rule 2 (expr)]
$default reduce using rule 2 (expr)
binop go to state 24
state 32
5 expr: ID '(' expr_list ')' .
5 expr: ID '(' expr_list ')' .
$default reduce using rule 5 (expr)
state 33
1 expr: . unop expr
2 | . expr binop expr
3 | . ID
4 | . ID '[' expr ']'
5 | . ID '(' expr_list ')'
6 | . ID '(' ')'
7 | . '(' expr ')'
8 | . INTCON
9 | . FLOATCON
11 expr_list: expr_list ',' . expr
12 unop: . '!'
ID shift, and go to state 1
INTCON shift, and go to state 2
FLOATCON shift, and go to state 3
'!' shift, and go to state 4
'(' shift, and go to state 5
expr go to state 35
unop go to state 7
state 34
4 expr: ID '[' expr ']' .
$default reduce using rule 4 (expr)
state 35
2 expr: expr . binop expr
11 expr_list: expr_list ',' expr . [')', ',']
13 binop: . AND_OP
14 | . OR_OP
15 | . EQ_OP
16 | . NEQ_OP
17 | . '+'
18 | . '-'
19 | . '*'
20 | . '/'
21 | . LEQ_OP
22 | . '<'
23 | . GEQ_OP
24 | . '>'
AND_OP shift, and go to state 12
OR_OP shift, and go to state 13
EQ_OP shift, and go to state 14
NEQ_OP shift, and go to state 15
LEQ_OP shift, and go to state 16
GEQ_OP shift, and go to state 17
'<' shift, and go to state 18
'>' shift, and go to state 19
'+' shift, and go to state 20
'-' shift, and go to state 21
'/' shift, and go to state 22
'*' shift, and go to state 23
$default reduce using rule 11 (expr_list)
binop go to state 24
FIX BY RICI BELOW:#
(Removed the unop and binop rules and enumerated them in the expr rule)
%token ID KEYWORD INTCON FLOATCON TYPE STRING
%token IF WHILE FOR VOID RETURN
%token AND_OP OR_OP EQ_OP NEQ_OP LEQ_OP GEQ_OP
%left "||"
%left "&&"
%nonassoc '<' "<=" '>' ">=" "==" "!="
%left '+' '-'
%left '/' '*'
%right '!'
%%
expr : ID
| ID '[' expr ']'
| ID '(' expr_list ')'
| ID '(' ')'
| '(' expr ')'
| INTCON
| FLOATCON
| '!' expr
| '-' expr
| expr '+' expr
| expr '-' expr
| expr '/' expr
| expr '*' expr
| expr '<' expr
| expr '>' expr
| expr "<=" expr
| expr ">=" expr
| expr "==" expr
| expr "!=" expr
| expr "&&" expr
| expr "||" expr
;
expr_list : expr
| expr_list ',' expr
;
%%
回答1:
Precedence only works if the productions directly include terminals named in the precedence declaration.
In other words, you cannot use expr: expr binop expr because the precedence relations can't help bison decide whether to shift the reduced binop non-terminal or reduce the expr on the top of the parse stack. Bison would have to know what the terminal inside the binop was, but it doesn't know that any more. (That's why reductions are called "reductions".)
To make it work, you have to write the productions out in full:
expr: expr '+' expr
| expr '-' expr
| expr '*' expr
|...
来源：https://stackoverflow.com/questions/19085340/bison-shift-reduce-error-for-c-like-language